Add renovate bot

[pokey]

• Migrate to a pnpm monorepo #1281
• Add basic tests for website and cheatsheet #1934
• Reopen Configure Renovate #1090
• Enable auto-merge for renovate PRs
• Configure renovate to bump pre-commit, ensuring that it remains in lockstep with prettier etc in package.json
• Look at Cleanup Typescript imports in pre-commit #640 (comment) to see if relevant here
• Force node.js version? Should match our @types/node version. Should figure out how it correlates to vscode node version. See also https://stackoverflow.com/a/29349773
• Pin vscode version to match engine version
• Figure out how to reapply our patch

  cursorless/package.json

  Line 49 in de37ebf

  "@docusaurus/theme-search-algolia@3.1.0": "patches/@docusaurus__theme-search-algolia@3.1.0.patch",

• Look at https://github.com/typescript-language-server/typescript-language-server/blob/master/renovate.json for inspiration
• Run dedupe after lockfile update using pnpmDedupe post-update option

[auscompgeek]

Looks like dependabot doesn't correctly bump pnpm lock files, despite GitHub announcing pnpm support earlier this year? Probably worth setting up renovate and disabling dependabot in this case.