refactor: clean Canny integration + rename 'Feedback' to 'Feature Requests' + improve TS doc page

[slorber]

Motivation

The existing Canny integration was a bit weird, as it used the 404 pages and redirected some subpaths to the canny board

We should be able to handle client-side routes better (not serving them with status 404) by using a simple CDN proxy config (widely available, except GitHub Pages...)

This is also an initial proof of concept showing that this is technically possible to do this correctly.

Later I'd like to document how to add client-side authenticated routes to a Docusaurus site, and maybe build a plugin for that.

Have you read the Contributing Guidelines on pull requests?

(Write your answer here.)

Test Plan

preview

[netlify]

✔️ [V2]

🔨 Explore the source changes: 6d55c10

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/611f753046dcb80007070aa5

😎 Browse the preview: https://deploy-preview-5389--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	77
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-5389--docusaurus-2.netlify.app/

[github-actions]

Size Change: +209 B (0%)

Total Size: 810 kB

Filename	Size	Change
website/build/assets/js/main.********.js	410 kB	+68 B (0%)
website/build/docs/index.html	43.1 kB	+43 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
website/.docusaurus/globalData.json	36.2 kB	0 B
website/build/assets/css/styles.********.css	93.7 kB	+3 B (0%)
website/build/blog/2017/12/14/introducing-docusaurus/index.html	65.3 kB	+16 B (0%)
website/build/blog/index.html	35.4 kB	+16 B (0%)
website/build/docs/installation/index.html	50.7 kB	+15 B (0%)
website/build/index.html	29.8 kB	+16 B (0%)
website/build/tests/docs/index.html	23.9 kB	+16 B (0%)
website/build/tests/docs/standalone/index.html	21.8 kB	+16 B (0%)

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