Add licensing and copyright information for all files in this repository. This
either happens in the file itself as a comment header or in the file
`.reuse/dep5`.
This commit also adds a Github workflow to check pull requests and adapts
copyright.pl to the changes.
Closes#8869
USe configure --with-ngtcp2 or --with-quiche
Using either option will enable a HTTP3 build.
Co-authored-by: Alessandro Ghedini <alessandro@ghedini.me>
Closes#3500