### 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
if (!have_plugins_changed) {
				for (int i = 0; i < enabled_plugins.size(); i++) {
					if (enabled_plugins.get(i).last_updated > last_custom_build_time) {
						have_plugins_changed = true;
						break;
					}
				}
			}
		}
		last_custom_build_time = OS::get_singleton()->get_unix_time();
		last_plugin_names = plugin_names;
		return have_plugins_changed || first_build;
	}
	String get_apk_expansion_fullpath(const Ref<EditorExportPreset> &p_preset, const String &p_path);
	Error save_apk_expansion_file(const Ref<EditorExportPreset> &p_preset, bool p_debug, const String &p_path);
	void get_command_line_flags(const Ref<EditorExportPreset> &p_preset, const String &p_path, int p_flags, Vector<uint8_t> &r_command_line_flags);
	Error sign_apk(const Ref<EditorExportPreset> &p_preset, bool p_debug, const String &export_path, EditorProgress &ep);
	void _clear_assets_directory();
	void _remove_copied_libs();
	static String join_list(const List<String> &p_parts, const String &p_separator);
	static String join_abis(const Vector<ABI> &p_parts, const String &p_separator, bool p_use_arch);
	virtual Error export_project(const Ref<EditorExportPreset> &p_preset, bool p_debug, const String &p_path, int p_flags = 0) override;
	Error export_project_helper(const Ref<EditorExportPreset> &p_preset, bool p_debug, const String &p_path, int export_format, bool should_sign, int p_flags);
	virtual void get_platform_features(List<String> *r_features) const override;
	virtual void resolve_platform_feature_priorities(const Ref<EditorExportPreset> &p_preset, HashSet<String> &p_features) override;
	EditorExportPlatformAndroid();
	~EditorExportPlatformAndroid();
};
#endif