Callbacks documentation doesn't contain all callbacks

[lauramurgatroyd]

Description

Some callbacks are missing, including CGLSEarlyStopping. This is particularly confusing because the notes in the CGLS docs reference it:

" in particular the CGLSEarlyStopping callback replicated the old behaviour."

https://tomographicimaging.github.io/CIL/nightly/optimisation/#cil.optimisation.algorithms.CGLS

Environment

import cil, sys
print(cil.version.version, cil.version.commit_hash, sys.version, sys.platform)