feat: video download support

[shpingalet007]

Standards checklist:

• The PR title is descriptive.
• The PR doesn't replicate another PR which is already open.
• The PR has self-explained commits history.
• The code is mine, or it's from somewhere with an Apache-2.0 compatible license.
• The code is efficient, to the best of my ability, and does not waste computer resources.
• The code is stable, and I have tested it myself, to the best of my abilities.
• If the code introduces new classes, methods, I provide a valid use case for all of them.

Changes:

• [...]

Other comments:

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[shpingalet007]

What is ready

• Peertube link generation for video download
• Working on any browser and Electron

TODO

• Electron doesn't show any UI to inform about the download process
• Check if Cordova works