Add mimetype application/x-lmdb
Since it shares the *.mdb extension with msaccess, added a tes file for msaccess, and gave a higher weight to the msaccess glob for compatibility reasons (so that filename-only matching of *.mdb still says msaccess). Reference for the extensions: https://lmdb.readthedocs.io/en/release/ Reference for the magic: https://git.openldap.org/openldap/openldap/-/blob/mdb.master/libraries/liblmdb/mdb.c Fixes: #168