Create LICENSE

[s-celles]

From https://github.com/MajicDesigns/MD_UISwitch/blob/master/docs/page_copyright.html

[MajicDesigns]

Why do you think it is necessary to include the licence? The type of licence is already mentioned in the .h file.

[per1234]

GitHub does have some neat features that are enabled by having a dedicated license file in the root of the repository. GitHub uses this file to detect the license of the repository and:

• Displays this on the info bar of the repository home page.
• Allows filtering searches by license type.
• Provides license information via the GitHub API.

https://help.github.com/articles/licensing-a-repository/

As for the license field in library.properties, there is some information here:
arduino/Arduino#6646 (comment)
Unfortunately there has not been any information from the Arduino team as to the official support for this field.

@scls19fr, since it looks like you're submitting a lot of this sort of PR I recommend you to start providing an explanation of why this is beneficial. That should prevent any confusion and make it more likely that your proposals will be accepted.