Add changelog to VS Code extension

[Weasy666]

VS Code provides extensions with a dedicated tab, in the extension's page, for changelogs, see following image.

It would be really nice, if rust-analyzer could make use of that feature. I don't know how difficult it is to take the same content, as is used at https://rust-analyzer.github.io/thisweek/2021/11/29/changelog-105.html, and also display it on the changelog tab, but it would be really nice to see the changes directly in VS Code, without the need to open a browser.

[lnicola]

Oof, we write the changelog after triggering the release.

[palfrey]

Docs are a little fuzzy on this, but indicate that you mostly just need a file like https://github.com/microsoft/vscode-cpptools/blob/main/Extension/CHANGELOG.md to make this work.

[joshka]

The code that displays the tab is https://github.com/microsoft/vscode/blob/b227e84a88ed27b9774ceb9aad3511c9c58b3dde/src/vs/workbench/contrib/extensions/browser/extensionEditor.ts#L600-L601