feat: export setAssetPath

[christian-bromann]

Ionicons never exports setAssetPath prevents users from actually changing given path. Exporting it makes Stencil to keep this function as part of the bundled runtime. I tested the change by using this HTML:

<script type="module" src="/node_modules/ionicons/dist/ionicons/ionicons.esm.js"></script>
<script type="module">
    import { setAssetPath } from '/node_modules/ionicons/dist/ionicons/index.esm.js';
    setAssetPath('/I/got/changed');
</script>
<ion-icon name="heart"></ion-icon>

I was able to verify that:

• I can import a setAssetPath method from ionicons
• it impacts where the SVGs are getting loaded from

Note: I have also reported this as a bug in Stencil

fixes #1302