Bug 27827: (follow-up) add a hint for clarification

Bug 27827: (follow-up) add a hint for clarification

When adding a new authority type, there is no indication of how big
the authority type code can be (auth_types.authtypecode in the DB has
a maximum length of 10 characters).

This patch fixes that.

To test, apply the patch and notice the hint appearing right above the
"Authority type:" text box as you add a new authority type: it should
display "10 characters maximum" in grey colour.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit c359c154364b0aa2aff0f368e21bd30e458173a9)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>