Incorporate Algolia-based search

[pepopowitz]

Addresses #633

This PR implements a local plugin hooking up Algolia docsearch. It is based on an external plugin that didn't quite work for our scenario. (Specifically, the search box only worked on initial page render, due to a known issue in that plugin.) I followed the lead of a comment on that issue, but moved all functionality into a local plugin instead of using the external one. We were only using about 12 lines of the external version, and about 30 lines were not working for us, so it felt wrong to keep using the external one.

In action

Things to note in the gif

• It takes you to the prod site when clicking on a result locally, I'm assuming because the URLs from algolia include the origin. A minor annoyance that I don't think is worth finding a way around, but let me know if you feel otherwise.
• The target URL includes #__gatsby at the end, again because it's in the Algolia URL. I'm not sure how it ends up there or how to get rid of it? I think it's probably just another minor annoyance.

Outdated information (kept here for posterity)

Original PR body

This PR adds a plugin for hooking up Algolia docsearch. Unfortunately, the plugin doesn't work very well for our scenario - it only connects the search box to Algolia on initial page render. As soon as you start clicking around the site, the search box becomes functionless. This is a known issue in that plugin. It is a result of our search box re-rendering at each new route, something the plugin doesn't account for. I dug a bit to try to fix it within the plugin so I could submit a PR, but I was unsuccessful.

Instead, I followed the lead of a comment on that issue. I'm still using the plugin to render the JS and CSS inclusions into the DOM, but connecting the actual search box with an effect in the SearchBox component.

As a result, we're only using about 12 lines of code from the plugin. In addition, we have to provide settings for the plugin to work, but they aren't actually used by the plugin (or the workaround - I don't think I can access the options for another plugin.) My preference at this point would be to ditch the plugin in favor of implementing those 12 lines ourselves, but I'd love to hear your opinions.

Remaining work on this PR:

• See what kind of styling I can do to the search results
• Ditch the plugin that only partially works for our scenario, in favor of implementing the few lines that do work in our own codebase. Maybe?
• Figure out how to get the algolia settings from gatsby-config.js.

[damassi]

My preference at this point would be to ditch the plugin in favor of implementing those 12 lines ourselves, but I'd love to hear your opinions.

I'm down with that! We can always iterate, same with the other current annoyances. An MVP with search is already a vast improvement over what we have.

[damassi]

👍

[pepopowitz]

I don't know how to make this plugin work with ES module syntax, but it isn't something that bothers me. If it bothers anyone else, maybe we could pair on it.

[damassi]

ES module syntax doesn't work completely in gatsby yet. Caused a bit of stress trying to figure that out when i was working on this before because it kinda worked at times, and was confusing.

[damassi]

@pepopowitz - is it possible to exclude certain pages from results? If so, can we remove the changelog page?

Otherwise, looks great 👍 Merge when ready and we can start looking more closely at how algolia indexes our pages.

[pepopowitz]

I think we can use a stop_urls setting to exclude them, but I have to figure out how/where to actually use that setting. I'll merge this and look into exclusions as follow-up work.

[artsyit]

🚀 PR was released in v7.1.1 🚀

[pepopowitz]

FYI @damassi I believe that this PR, when merged, should remove the changelog from our search results.