[Feature] Change a few strings

[jwkwshjsjsj]

Describe the feature

"Material you" —> "Material You"

"GitHub Repository" in the description of "Check for updates"

Remove the period from the description of "Beta releases" for consistency with many other settings that do not have this

"Update yt-dl to the new version" —> "Update yt-dlp"

Reword the description of "Update yt-dl to the new version" to be less confusing. Currently it is "Useful tip while downloading updates". While downloading what updates?

I think the non-first items in lists of settings items in a category should have begin with a lowercase letter
"Theme, Accents, Preferred search engine" —> "Theme, accents, preferred search engine" for example

"Nico video" —> "Niconico"

"Yahoo screen" —> "Yahoo Screen"

Reason for adding

I think the proposed changes would be better.

Example(s)

No response

Additional context

No response