[enh] #134: Introduce insert-license pre-commit-hook

.pre-commit-config.yaml

@@ -3,3 +3,11 @@ repos:
     rev: 21.5b0
     hooks:
     - id: black
+-   repo: https://github.com/Lucas-C/pre-commit-hooks
+    rev: v1.1.10
+    hooks:
+    -   id: insert-license
+        files: \.py$
+        args:
+        - --license-filepath
+        - license_header.txt

license_header.txt

+Copyright  2014-2021 Vincent Texier <vit@free.fr>
+
+DuniterPy 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.
+
+DuniterPy 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/>.