```diff blocks in Docs are not rendered #612

Previously, diff blocks in the docs would work well. But now, see for example https://remotion.dev/docs/javascript#upgrading, the diffs are rendered as plaintext. We need to go through the commits and see where it broke, and fix it (this might need a fix in a third-party package!)

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Approval criteria for this PR:

• Fix the rendering of the diff.

Note: This might need a fix in a third-party library. We will accept your contribution for Hacktoberfest regardless of if they merge it - in the worst case let's make a node_modules patch for our docs.