ci(github): update github actions and dtslint to latest

[ChristianMurphy]

dependency updates may help resolve flaky tests which have been occuring on next branch.

dtslint updated using yarn upgrade dtslint

related to #1172

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://vercel.com/mdx/mdx/6wucdp5sl
✅ Preview: https://mdx-git-fork-christianmurphy-v2-github-actions-dtslint-update.mdx.vercel.app

[ChristianMurphy]

@johno there is still a test error, but in the unit tests, and it appears to be unrelated to these changes

1..166
# tests 166
# pass  153
# fail  13

see https://github.com/mdx-js/mdx/pull/1178/checks?check_run_id=900934958 for full details.

[johno]

Oh weird, yeah looks like it might be a cross-platform issue, we can dig into that later. Thank you for the updates for types, let's see if that makes things more stable!