Updated ReadMe + Enhanced Feature Sets

[Misunderstood-Wookiee]

• Container edges have rounded corners for a modern UI style.
• C# Scripts updated with new media type Fanart-Background for LaunchBox and I think incorporated into Emulation Station correctly, we were unsure of the correct implementation for that so might wish to double-check it.
• New UWP App Icon.
• RetroPass UI and Box Art Rows scale dynamically.
• RetroPass Game Grid brush made transparent for better visual box art display.
• Add Future Support for Flycast Stand-Alone.
• Add Future Support for PPSSPP Stand-Alone.
• Add Future Support for DuckStation Stand-Alone (Dev Mode (Brazil)
• ReadMe.md has been amended with additional grammatical/context changes & explains how to use optional supported emulators.

*Emulator Support will require URI support added to relevant repositories so the code exists here to help future support. *Media Type is currently unused in layout pages, will remedy in a future PR

[Misunderstood-Wookiee]

Ignore the commit for AeatherSX2, this commit was reverted further down the chain. I suggest cherry-picking the squashed https://github.com/retropassdev/RetroPass/pull/27/commits/4d46061f9c96d9b058bc810964ab353dd07863cd This PR includes #26 and further enhancement of #26 Sorry about the slightly dis-organised commits.