Minor rewording and grammar fix

It'll be better if "**Translation**" in the header gets changed to "**Translations**", and "**With the support of youtube-dl and our browser extensions, you can also play a variety of online streams in IINA via one click.**" gets changed to "**With the support of youtube-dl and our browser extensions, you can also play a variety of online streams via one click in IINA.**"

😎