Rename MP3File to WAVFile, as now using wav files

Also fix DarkMode.  Previously it wouldn't matter what was specified in
the config file for Eye-Reminder, we always used light mode.

main.go

@@ -27,14 +27,14 @@ import (
 const (
 	DEFAULT_TIME_INBETWEEN_NOTIFICATIONS = 20 * time.Minute
 	EYE_REMINDER_ICON_URL                = "https://gitea.ronald1985.uk/ronald1985/Eye-Reminder/raw/branch/master/assets/Eye-Reminder-Icon.png"
-	DEFAULT_CONFIG_FILE                  = "Interval: 20\nSoundEnabled: false\nMP3File: \"\"\nDarkTheme: true"
+	DEFAULT_CONFIG_FILE                  = "Interval: 20\nSoundEnabled: false\nWAVFile: \"\"\nDarkTheme: true"
 )
 
 type Config struct {
 	Interval      int    `yaml:"Interval"`
 	SoundEnabled  bool   `yaml:"SoundEnabled"`
-	WAVFile       string `yaml:"MP3File"`
-	darkTheme     bool   `yaml:"DarkTheme"`
+	WAVFile       string `yaml:"WAVFile"`
+	DarkTheme     bool   `yaml:"DarkTheme"`
 	imageLocation string
 }
 
@@ -202,7 +202,7 @@ func systrayOnReady() {
 	)
 	systray.AddSeparator()
 	mDarkThemeEnabled := systray.AddMenuItemCheckbox(
-		"Dark mode enabled", "Whether the dark theme icons are used", ProgramConfig.darkTheme,
+		"Dark mode enabled", "Whether the dark theme icons are used", ProgramConfig.DarkTheme,
 	)
 	systray.AddSeparator()
 	mQuitOrig := systray.AddMenuItem("Quit", "Quit the whole app")
@@ -229,7 +229,7 @@ func systrayOnReady() {
 
 					mStopSound.Enable()
 
-					if ProgramConfig.darkTheme {
+					if ProgramConfig.DarkTheme {
 						systray.SetIcon(lightmusicicon.Data)
 					} else {
 						systray.SetIcon(darkmusicicon.Data)
@@ -285,7 +285,7 @@ func systrayOnReady() {
 			case <-mStopSound.ClickedCh:
 				stopSound = true
 			case <-mDarkThemeEnabled.ClickedCh:
-				ProgramConfig.darkTheme = !ProgramConfig.darkTheme
+				ProgramConfig.DarkTheme = !ProgramConfig.DarkTheme
 
 				if mDarkThemeEnabled.Checked() {
 					mDarkThemeEnabled.Uncheck()