add variable mapping to CI

[larsbuntemeyer]

We should add this gist to the CI to keep the variable mapping up to date. Maybe the mapping could be another column in the cmor-table.csv. This would create the possiblity to catch inconsistencies early.

[larsbuntemeyer]

see #82

[larsbuntemeyer]

Another gist here: https://gist.github.com/matthew-mizielinski/3103beb41e2b83a51b7ae923592489cf