release: bump to 3.1.0 and add its changelog

Bump versionCode to 14 and versionName to 3.1.0, and add the
changelogs/14.txt release notes covering ReplayGain, artist pages,
sort names, keep-screen-on and the fixes.

No tag: this only prepares the release.

app/build.gradle.kts

@@ -36,8 +36,8 @@ android {
         applicationId = "com.subtracks"
         minSdk = 24
         targetSdk = 37
-        versionCode = 13
-        versionName = "3.0.0"
+        versionCode = 14
+        versionName = "3.1.0"
         buildConfigField("String", "COMMIT_HASH", "\"$commitHash\"")
     }
 

metadata/en-US/changelogs/14.txt

@@ -0,0 +1,12 @@
+- ReplayGain: loudness from server tags, with Auto, track, album, off, preamp
+- Artist pages: bio, art, credits and appearances
+- Sort lists: regular names or sort names
+- Improved handling for multi-artist albums/tracks
+- Keep the screen on while now playing is open setting, off by default (thanks @chiangww!)
+
+Fixed
+
+- Notification progress for unknown-length streams (Opus/Ogg)
+- Now playing artwork and shadow fixes
+
+Release notes: https://github.com/austinried/subtracks/releases/tag/v3.1.0