[Trivial] Change single quotes to double quotes (#40)

### What changed? Why?
Change single quotes to double quotes in README

#### Qualified Impact
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README.md

@@ -69,8 +69,8 @@ require 'coinbase'
 To start, [create a CDP API Key](https://portal.cdp.coinbase.com/access/api). Then, initialize the Platform SDK by passing your API Key name and API Key's private key via the `configure` method:
 
 ```ruby
-api_key_name = 'Copy your API Key name here.'
-api_key_private_key = 'Copy your API Key\'s private key here.'
+api_key_name = "Copy your API Key name here."
+api_key_private_key = "Copy your API Key's private key here."
 
 Coinbase.configure do |config|
   config.api_key_name = api_key_name

docs/file.README.html

@@ -124,8 +124,8 @@ <h3 id="label-Initialization">Initialization</h3>
 
 <p>To start, <a href="https://portal.cdp.coinbase.com/access/api">create a CDP API Key</a>. Then, initialize the Platform SDK by passing your API Key name and API Key&#39;s private key via the <code>configure</code> method:</p>
 
-<pre class="code ruby"><code class="ruby"><span class='id identifier rubyid_api_key_name'>api_key_name</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&#39;</span><span class='tstring_content'>Copy your API Key name here.</span><span class='tstring_end'>&#39;</span></span>
-<span class='id identifier rubyid_api_key_private_key'>api_key_private_key</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&#39;</span><span class='tstring_content'>Copy your API Key\&#39;s private key here.</span><span class='tstring_end'>&#39;</span></span>
+<pre class="code ruby"><code class="ruby"><span class='id identifier rubyid_api_key_name'>api_key_name</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&quot;</span><span class='tstring_content'>Copy your API Key name here.</span><span class='tstring_end'>&quot;</span></span>
+<span class='id identifier rubyid_api_key_private_key'>api_key_private_key</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&quot;</span><span class='tstring_content'>Copy your API Key&#39;s private key here.</span><span class='tstring_end'>&quot;</span></span>
 
 <span class='const'><span class='object_link'><a href="Coinbase.html" title="Coinbase (module)">Coinbase</a></span></span><span class='period'>.</span><span class='id identifier rubyid_configure'><span class='object_link'><a href="Coinbase.html#configure-class_method" title="Coinbase.configure (method)">configure</a></span></span> <span class='kw'>do</span> <span class='op'>|</span><span class='id identifier rubyid_config'>config</span><span class='op'>|</span>
   <span class='id identifier rubyid_config'>config</span><span class='period'>.</span><span class='id identifier rubyid_api_key_name'>api_key_name</span> <span class='op'>=</span> <span class='id identifier rubyid_api_key_name'>api_key_name</span>

docs/index.html

@@ -124,8 +124,8 @@ <h3 id="label-Initialization">Initialization</h3>
 
 <p>To start, <a href="https://portal.cdp.coinbase.com/access/api">create a CDP API Key</a>. Then, initialize the Platform SDK by passing your API Key name and API Key&#39;s private key via the <code>configure</code> method:</p>
 
-<pre class="code ruby"><code class="ruby"><span class='id identifier rubyid_api_key_name'>api_key_name</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&#39;</span><span class='tstring_content'>Copy your API Key name here.</span><span class='tstring_end'>&#39;</span></span>
-<span class='id identifier rubyid_api_key_private_key'>api_key_private_key</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&#39;</span><span class='tstring_content'>Copy your API Key\&#39;s private key here.</span><span class='tstring_end'>&#39;</span></span>
+<pre class="code ruby"><code class="ruby"><span class='id identifier rubyid_api_key_name'>api_key_name</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&quot;</span><span class='tstring_content'>Copy your API Key name here.</span><span class='tstring_end'>&quot;</span></span>
+<span class='id identifier rubyid_api_key_private_key'>api_key_private_key</span> <span class='op'>=</span> <span class='tstring'><span class='tstring_beg'>&quot;</span><span class='tstring_content'>Copy your API Key&#39;s private key here.</span><span class='tstring_end'>&quot;</span></span>
 
 <span class='const'><span class='object_link'><a href="Coinbase.html" title="Coinbase (module)">Coinbase</a></span></span><span class='period'>.</span><span class='id identifier rubyid_configure'><span class='object_link'><a href="Coinbase.html#configure-class_method" title="Coinbase.configure (method)">configure</a></span></span> <span class='kw'>do</span> <span class='op'>|</span><span class='id identifier rubyid_config'>config</span><span class='op'>|</span>
   <span class='id identifier rubyid_config'>config</span><span class='period'>.</span><span class='id identifier rubyid_api_key_name'>api_key_name</span> <span class='op'>=</span> <span class='id identifier rubyid_api_key_name'>api_key_name</span>