Merge pull request #2 from Neotron-Compute/bugfix/fix-link-to-licence

Add text of GPL3, and correct Cargo.toml file.

Author: thejpster

Cargo.toml

@@ -2,7 +2,7 @@
 authors = ["Jonathan 'theJPster' Pallant <github@thejpster.org.uk>"]
 edition = "2018"
 readme = "README.md"
-license = "GPLv3"
+license = "GPL-3.0-or-later"
 name = "neotron-pico-bios"
 version = "0.1.0"