### Godot version

3.5.1.stable, v4.0.beta.custom_build [0a87ead64]

### System information

Ubuntu 22.04.1

### Issue description

For example, if project has name "300spartans", we can't enter the "org.godotengine.300spartans" to "Unique Name" field. We get the error "Invalid package name: A digit cannot be the first character in a package segment". But , if we enter "org.godotengine.$genname", there will be no error message. When exporting, the name will be set as "org.godotengine.spartans" without "300" in beginning, but user will not be informed about it. I think, it is not very good. It may not be worth making changes to the source code, but mention it in the documentation.

### Steps to reproduce

See issue description.

### Minimal reproduction project

N/A
"SUBSCRIBED_FEEDS_WRITE",
	"SYSTEM_ALERT_WINDOW",
	"TRANSMIT_IR",
	"UNINSTALL_SHORTCUT",
	"UPDATE_DEVICE_STATS",
	"USE_CREDENTIALS",
	"USE_SIP",
	"VIBRATE",
	"WAKE_LOCK",
	"WRITE_APN_SETTINGS",
	"WRITE_CALENDAR",
	"WRITE_CALL_LOG",
	"WRITE_CONTACTS",
	"WRITE_EXTERNAL_STORAGE",
	"WRITE_GSERVICES",
	"WRITE_HISTORY_BOOKMARKS",
	"WRITE_PROFILE",
	"WRITE_SECURE_SETTINGS",
	"WRITE_SETTINGS",
	"WRITE_SMS",
	"WRITE_SOCIAL_STREAM",
	"WRITE_SYNC_SETTINGS",
	"WRITE_USER_DICTIONARY",
	nullptr
};
static const char *SPLASH_IMAGE_EXPORT_PATH = "res/drawable-nodpi/splash.png";
static const char *LEGACY_BUILD_SPLASH_IMAGE_EXPORT_PATH = "res/drawable-nodpi-v4/splash.png";
static const char *SPLASH_BG_COLOR_PATH = "res/drawable-nodpi/splash_bg_color.png";
static const char *LEGACY_BUILD_SPLASH_BG_COLOR_PATH = "res/drawable-nodpi-v4/splash_bg_color.png";
static const char *SPLASH_CONFIG_PATH = "res://android/build/res/drawable/splash_drawable.xml";