feat(theme): add versions attribute to docsVersionDropdown navbar item

[hrumhurum]

Motivation

Fix #10833

The docsVersionDropdown navbar item supports a new versions attribute to filter/whitelist displayed versions. Only the provided versions will be displayed.

Example:

{
  type: 'docsVersionDropdown',
  versions: ['1.0.1', '2.1.1']
},

Also gives the ability to override version attributes (for now, only display label) by providing an object.

{
  type: 'docsVersionDropdown',
  versions: {
  '1.0.1': {label: '1.x'},
  '2.1.1': {label: '2.x'},
},

Test Plan

1. Go to the deploy preview website
2. Locate the docs version dropdown in the upper part of the website
3. Click on the dropdown
4. Notice how the version titles are customized
5. Notice how the list of versions are customized to display just a subset of versions
6. Visit Docusaurus documentation preview to take a look at the documentation for new functionality

Test links

Deploy preview: https://gp-temp-docusaurus-app1.netlify.app/eazfuscator.net

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⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🔴 33	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🔴 49	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 72	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 62	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🟠 62	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 63	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 74	🟢 100	🟢 100	🟠 86	Report

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[slorber]

The feature works thanks 👍

But I'd like a few things changed

[slorber]

Hmmm that looks a bit complicated to me.

Here's some pseudo-code I'd write to normalize the 3 cases under a single one:

type VersionConfig = {
  label?: string
}

type VersionItem = {
  version: GlobalVersion,
  config?: VersionConfig
}

function getDropdownVersions({versions,item)}): VersionItem[] {
  const versionMap = new Map<string, GlobalVersion>(
    versions.map((version) => [version.name, version]),
  );

  if ( item.versions ) {
    // Maybe fail-fast if the user provide version names that do not exist
    // But it's preferable to do this earlier in Node.js side, if possible
 
    if (Array.isArray(item.versions)) {
      return item.versions.map(name => ({
        version: versionMap[name],
        config: undefined;
      }));
    }
    else {
      // pseudo code: in practice, we don't want to import Lodash in theme code
      return _.mapValues(item.versions,(config,name) => ({
        version: versionMap[name],
        config,
      }));
    }
  }
  else {
    return versions.map(v => ({version, config: undefined})
  }
}

[hrumhurum]

The reason why the code is built like that is to keep the complexity in m + n domain instead of m * n. There are two actual phases:

1. Getting configuration from 2 types of sources (string[] and PropVersionItems). This gives us n complexity
2. Applying configuration to versions. This gives us m complexity

If I refactor the code the way you suggest (mesh up two phases in m * n fashion), I clearly hit the problem at the // Maybe fail-fast if the user provide version names that do not exist stage, because I would need to duplicate that logic for two different types of configuration sources: string[] and PropVersionItems.

I know why you made this suggestion, it actually represents my first implementation prototype. But when I did hit a code duplication problem I had to split the logic into two clean phases to avoid m * n complexity.

[slorber]

I'm not sure exactly what you mean here but I'm pretty sure I'll be able to simplify your code before merging while keeping the same behavior. If you don't find a way, I'll work on it.

[slorber]

Still think we shouldn't include the "version name/label shortcut" in this PR, and discuss it independently in another proposal.

Let me know if you can simplify your code, otherwise I'll do it

[slorber]

I'm not sure exactly what you mean here but I'm pretty sure I'll be able to simplify your code before merging while keeping the same behavior. If you don't find a way, I'll work on it.