docs for deploying with gzip

[nattaylor]

I think it might be nice to add a section to https://docs.datasette.io/en/stable/deploying.html about using gzip, since it results in smaller payloads and faster response times.

ntaylor@ntaylor-mac ~ % curl -s 'https://data.nattaylor.com/d/records.json?sql=select+body+from+records' -o/dev/null -w '%{size_download} %{time_total}'
534033 0.486674%

# Add to .htaccess: AddOutputFilterByType DEFLATE application/json                                                                                                                                                                                                                                                                         ntaylor@ntaylor-mac ~ % curl -s -H "Accept-Encoding: gzip" 'https://data.nattaylor.com/d/records.json?sql=select+body+from+records' -o/dev/null -w '%{size_download} %{time_total}'
77553 0.288803%                                                                                                                                                                                                                             ```