Added UI assets

— background banners for “player in check”, “pawn promotion”, “piece
graveyard”, and “player header”

—new backgrounds have rounded corners, better color schemes, and
gradients
Fixed various text issues

—changed certain black text renders to more pleasing grey

—centered “One Player Options” header

—changed button select color to blue to match overall color scheme
Fixed gameplay screen background bug

—gameplay screen now renders correctly with solid background

—background color changed to more pleasant grey color
Changed backsplash aspect ratio

—backsplash now has correct dimensions
Added improved UI elements to game screen

—rounded corners, gradients, improved colors for player headers and
piece graveyards
Added improved "Player in Check" banner
Added end of game banner/message

—when the game concludes, there is now a notification banner stating
the winner
Added pawn promotion banner to game screen

—pawn promotion now displays over game screen
—UI elements for pawn promotion improved
**Segmentation fault upon promotion (needs fixing)
Fixed pawn promotion Seg fault
Fixed En Passant move

—this special move now works correctly
Fixed "pawn open move jump"

—previously a pawn would be able to jump a piece directly in front of
it if the move was the pawns first; this is fixed.
ignore
Merge branch 'Ryan_UI_Improvements'