Add Osu! 2021.320.0 (#9039)

manifests/Peppy/Osu!/2021.320.0.yaml

@@ -0,0 +1,17 @@
+Id: Peppy.Osu!
+Name: Osu!
+Publisher: Dean "peppy" Herbert
+AppMoniker: osu
+Description: "A free-to-win rhythm game developed by peppy with four game modes: osu!standard, a circle clicking simulator; osu!taiko, a drumming emulator; osu!catch, a fruit salad catcher; and osu!mania, a key smashing synthesizer."
+Homepage: https://osu.ppy.sh/
+Version: 2021.320.0
+License: MIT
+LicenseUrl: https://github.com/ppy/osu/blob/master/LICENCE
+Installers:
+  - Arch: x64
+    Url: https://github.com/ppy/osu/releases/download/2021.320.0/install.exe
+    Sha256: d56d5b09c37c6fc754026be5b16538f590c91830f9393f3a8b0bb05a94e1e553
+    InstallerType: exe
+    Switches:
+      Silent: /silent
+      SilentWithProgress: /silent