### 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
return p_export_format == EXPORT_FORMAT_AAB ? AAB_ASSETS_DIRECTORY : APK_ASSETS_DIRECTORY;
}
bool EditorExportPlatformAndroid::is_package_name_valid(const String &p_package, String *r_error) const {
	String pname = p_package;
	if (pname.length() == 0) {
		if (r_error) {
			*r_error = TTR("Package name is missing.");
		}
		return false;
	}
	int segments = 0;
	bool first = true;
	for (int i = 0; i < pname.length(); i++) {
		char32_t c = pname[i];
		if (first && c == '.') {
			if (r_error) {
				*r_error = TTR("Package segments must be of non-zero length.");
			}
			return false;
		}
		if (c == '.') {
			segments++;
			first = true;
			continue;
		}
		if (!is_ascii_identifier_char(c)) {
			if (r_error) {
				*r_error = vformat(TTR("The character '%s' is not allowed in Android application package names."), String::chr(c));
			}
			return false;