Resolve "add licence"

Closes #47 (closed)

LICENSE

+Copyright (c) 2021-present Lydra
+
+Portions of this software are licensed as follows:
+
+- The graphic charter (logo, association of colors and fonts) is not under free license and belongs to Oxalis - Lydra.
+- All content residing under the "docs/" directory of this repository is licensed under "Creative Commons: CC BY-SA 4.0 license".
+- Content outside of the above mentioned directories or restrictions above is available under the MIT license as defined below.
+
+---
+
+MIT License
+
+Copyright (c) 2021 Christophe Chaudier
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.