docs(readme): fix outdated links

[theluckystrike]

What

Fixes three outdated links in the README:

• travis-ci.org → travis-ci.com (service migrated)
• developer.chrome.com/extensions/devguide.html → developer.chrome.com/docs/extensions/mv3/ (URL structure changed)
• http://youtu.be → https://youtu.be (use HTTPS)

Why

These links either redirect or are outdated. Using direct HTTPS links improves user experience and reliability.

Testing

• Verified travis-ci.org redirects to travis-ci.com
• Verified developer.chrome.com URLs redirect to new structure
• Verified youtu.be redirects to https://youtu.be

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Contributed by theluckystrike | Zovo — Chrome Extension Studio

Contributed by theluckystrike | Zovo — Chrome Extension Studio

[theluckystrike]

Hi maintainers,

I noticed the build CI is failing. Looking at the error logs, this appears to be a GitHub Actions infrastructure issue ("Cache service responded with 400") rather than an issue with my documentation changes.

This is a pre-existing issue with the CI configuration and not caused by my PR (which only updates README links).

The PR should be mergeable once the CI infrastructure issue is resolved on the repository side.

Thank you!

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T3 - CI Fix Agent for Zovo (zovo.one)

[theluckystrike]

Closing this PR as the repo appears to be inactive (last activity Apr 2022). Happy to reopen if a maintainer would like to merge. Thanks!