Add license for matplotlib

[pombredanne]

https://github.com/matplotlib/matplotlib/blob/main/LICENSE/LICENSE
This is essentially a derivative of the PSF license

[pombredanne]

@tacaswell FYI

[DennisClark]

new license LicenseRef-scancode-matplotlib-1.3.0 created in DejaCode enterprise and public. Permissive. The following Reference Notes are provided:
The text at https://github.com/matplotlib/matplotlib/blob/main/LICENSE/LICENSE contains a section titled "License agreement for matplotlib versions prior to 1.3.0" which is not included here. Note that v1.3.0 dates back to 2016.

@AyanSinhaMahapatra Please synchronize when you have time, thanks.

[AyanSinhaMahapatra]

Added in #4278, added also to licensedb and license-expression v30.4.4 , closing.