add: gpl v3 license footer

README.md

@@ -1,6 +1,8 @@
 # Fuji-Fabric
 ![github workflow build job](https://img.shields.io/github/actions/workflow/status/sakurawald/fuji-fabric/build.yml)
 ![github license](https://img.shields.io/github/license/sakurawald/fuji-fabric)
+![github commits since latest release](https://img.shields.io/github/commits-since/sakurawald/fuji-fabric/latest)
+![modrinth download counter](https://img.shields.io/modrinth/dt/1TowMm2v)
 
 ## Description
 Fuji is a minecraft mod that provides many essential and useful modules for vanilla survival.
@@ -17,19 +19,30 @@ Fuji is a minecraft mod that provides many essential and useful modules for vani
 3. **High-Performance**: Keep performance in mind while coding. (From data-structure, algorithm, lazy-evaluation and cache to improve performance greatly.)
 4. **Easy-to-Use**: a text-based per-field-explained auto-generated always-up-to-date documentation is provided. (Our configuration use lots of mini-language and generators to provide a unified setup.)
 
-## Wiki
+## Documentation
 See [configuration](https://github.com/sakurawald/fuji-fabric/wiki/Configuration)
 
 See [permission](https://github.com/sakurawald/fuji-fabric/wiki/Permission)
 
 See [faq](https://github.com/sakurawald/fuji-fabric/wiki/FAQ)
 
 ## Reference
-At the early stage of this project, we reference some source and ideas from the following projects:
-1. https://www.zrips.net/cmi/
-2. https://essentialsx.net/
-3. https://v2.nucleuspowered.org/
-3. https://modrinth.com/mod/essential-commands
-4. https://modrinth.com/mod/skinrestorer
-5. https://modrinth.com/mod/headindex
-6. https://modrinth.com/mod/sit
+See [reference](https://github.com/sakurawald/fuji-fabric/blob/dev/REFERENCE)
+
+## License
+```
+Copyright (C) 2023  [email protected]
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+```

REFERENCE

@@ -0,0 +1,8 @@
+We reference source and ideas from the following projects:
+- https://www.zrips.net/cmi/
+- https://essentialsx.net/
+- https://v2.nucleuspowered.org/
+- https://modrinth.com/mod/essential-commands
+- https://modrinth.com/mod/skinrestorer
+- https://modrinth.com/mod/headindex
+- https://modrinth.com/mod/sit