misc: show only latest archive alpha/beta versions dropdown

[lex111]

Motivation

Currently versions dropdown on the site is quite long, I propose to reduce its items by showing only the latest archived versions, since all available versions already renders on the "Versions" page.

Have you read the Contributing Guidelines on pull requests?

Yes

Test Plan

Preview.

Related PRs

(If this PR adds or changes functionality, please take some time to update the docs at https://github.com/facebook/docusaurus, and link to your PR here.)

[netlify]

✔️ [V2]

🔨 Explore the source changes: 5a3a3e8

🔍 Inspect the deploy log: https://app.netlify.com/sites/docusaurus-2/deploys/6182afb80f12dd000738ec3e

😎 Browse the preview: https://deploy-preview-5862--docusaurus-2.netlify.app

[github-actions]

⚡️ Lighthouse report for the changes in this PR:

Category	Score
🟠 Performance	88
🟢 Accessibility	98
🟢 Best practices	100
🟢 SEO	100
🟢 PWA	95

Lighthouse ran on https://deploy-preview-5862--docusaurus-2.netlify.app/

[github-actions]

Size Change: -19.3 kB (-2%)

Total Size: 832 kB

Filename	Size	Change
website/build/assets/js/main.********.js	425 kB	-654 B (0%)
website/build/blog/2017/12/14/introducing-docusaurus/index.html	66.1 kB	-2.66 kB (-4%)
website/build/blog/index.html	36.8 kB	-2.66 kB (-7%)	✅
website/build/docs/index.html	44 kB	-2.66 kB (-6%)	✅
website/build/docs/installation/index.html	51.5 kB	-2.66 kB (-5%)	✅
website/build/index.html	29.5 kB	-2.66 kB (-8%)	✅
website/build/tests/docs/index.html	25.2 kB	-2.66 kB (-10%)	👏
website/build/tests/docs/standalone/index.html	21.7 kB	-2.66 kB (-11%)	👏

ℹ️ View Unchanged

Filename	Size
website/.docusaurus/globalData.json	38 kB
website/build/assets/css/styles.********.css	94 kB

_{compressed-size-action}

[Josh-Cena]

What's the rationale to keep the last Alpha release? The alpha-beta cutoff was pretty arbitrary iirc, and beta.0 is not much different from alpha.75. From the NPM stats it doesn't seem alpha versions are very popular either

Also, surprised to see such significant bundle size optimization👀

[slorber]

Agree that it's not so useful to keep the latest alphas.
I'd rather keep the last 5 archived versions in the dropdown + 1.x.
Other versions remain available on the "All Versions" page anyway.
It's probably worth creating a const ArchivedVersionsDropdownItems

Also, surprised to see such significant bundle size optimization👀

I don't understand either, would be interesting to investigate and see a diff

[lex111]

I'd rather keep the last 5 archived versions in the dropdown + 1.x.

There won't be any alpha version in dropdown, alright then, but maybe we shouldn't create extra var for this?

[slorber]

Looks good enough for now thanks 👍

[slorber]

FYI about the file size diff: #5865