Change LICENSE from GPL to LGPL (#25)

* Change LICENSE from GPL to LGPL

This done with the consent of all code authors.

Also add copyright notice to README

* Drop Python 3.8 as it is EoL and setuptools 77 needs 3.9+

Author: connorjward

.github/workflows/ci.yml

@@ -20,7 +20,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13']
+        python: ['3.9', '3.10', '3.11', '3.12', '3.13']
         os: [ubuntu-latest, macos-latest, windows-latest]
         mpi: [mpich, openmpi, msmpi]
         exclude: