Adding the ability to download channel videos

[Bazsalanszky]

This PR contains a small patch that allows the user to download all of the videos of a given channel as requested in #270. It works the same way as downloading group videos.

[lukaarma]

@snobu can we update the actions to run on pull requests too?

@Bazsalanszky as soon as I have more free time I'll pull this, test it and I'll let you know.

[privacywhen]

This was very helpful for me, thank you.

[Xelus22]

I'm having trouble trying to run this command.

./destreamer.sh -i "https://web.microsoftstream.com/channel/some-numbers" -k
Access token still good for 54 minutes.

Parsing video/group urls

[WARNING] Invalid url 'https://web.microsoftstream.com/channel/some-numbers', skipping..
Fetching videos info...

edit: nvm i forgot to run npm run build

edit2: works great! also on v3 as well

[soumdtt]

For some reason, I am having trouble downloading group videos. Invalid URL is issued.... I had run nom run build