Add Flathub download button and Flatpak manifest #93684

Job	Run time
skip-duplicates-code	6s
skip-duplicates-code	6s
matrix-variables	1s
matrix-variables	1s
skip-duplicates-data	6s
skip-duplicates-data	6s
Basic Build and Test (Clang 10, Ubuntu, Curses)	52m 19s
Basic Build and Test (Clang 10, Ubuntu, Curses)	54m 45s
Clang 14, macOS 12, Tiles, Sound, x64 and arm64 Universal Binary	1s
Clang 14, macOS 12, Tiles, Sound, x64 and arm64 Universal Binary	1h 17m 38s
GCC 9, Curses, LTO	1s
GCC 9, Curses, LTO	35m 14s
Clang 12, Ubuntu, Tiles, ASan	1s
Clang 12, Ubuntu, Tiles, ASan	1s
GCC 11, Ubuntu, Curses, ASan	1s
GCC 11, Ubuntu, Curses, ASan	1s
GCC 12, Ubuntu cross-compile to MinGW-Win64, Tiles, Sound	1s
GCC 12, Ubuntu cross-compile to MinGW-Win64, Tiles, Sound	1s
GCC 9, Ubuntu, Tiles, Sound, CMake	1s
GCC 9, Ubuntu, Tiles, Sound, CMake	1s
emscripten	0s
emscripten	0s
	3h 40m 32s

Provide feedback