Add setting for subtitle outline size (#375)

Adds a settings allowing for adjusting the thickness of unstyled
subtitle outlines, if outline is enabled.

This is applied for both ExoPlayer & MPV

Closes #179

![outline
Large](https://github.com/user-attachments/assets/dfef74a5-a4d4-49db-a8d2-231e46ab151e)

Dev note: the ExoPlayer implementation is bad code, don't write code
like this. It works though

app/src/main/java/com/github/damontecres/wholphin/services/AppUpgradeHandler.kt

@@ -163,4 +163,14 @@ suspend fun upgradeApp(
             }
         }
     }
+
+    if (previous.isEqualOrBefore(Version.fromString("0.3.5-0-g0"))) {
+        appPreferences.updateData {
+            it.updateSubtitlePreferences {
+                if (edgeThickness < 1) {
+                    edgeThickness = SubtitleSettings.EdgeThickness.defaultValue.toInt()
+                }
+            }
+        }
+    }
 }