Add visualize_mcap example

[oxkitsune]

What

This adds a new example that showcases the ability to ingest MCAP and visualize custom message types using component mapping!

The data visualized was an MCAP file that we already have in the repository, and was generated from a modified version of the Trossen Arm MuJoCo simulation.

[github-actions]

Web viewer built successfully.

Result	Commit	Link	Manifest
✅	ac52b42	https://rerun.io/viewer/pr/12668	+nightly +main

View image diff on kitdiff.

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[github-actions]

Latest documentation preview deployed successfully.

Result	Commit	Link
✅	ac52b42	https://landing-o2aha0ca3-rerun.vercel.app/docs

^{Note: This comment is updated whenever you push a commit.}

[oxkitsune]

@rerun-bot reality-sync

[rerun-sync]

Sync complete. Mirror PR in reality: https://github.com/rerun-io/reality/pull/881

Triggered by @oxkitsune

[rerun-sync]

❌ Reality sync failed

The reality-sync workflow encountered an error. Please check the workflow logs for details.

Common fix: Try rebasing your PR on the latest main branch:

git fetch origin main
git rebase origin/main
git push --force-with-lease

Then re-run @rerun-bot reality-sync.

Triggered by @oxkitsune