[FIX] README template section levels

[dreispt]

The README generation could return an error like this:

  docutils.utils.SystemMessage: account_avatax/README.rst:349: (SEVERE/4)
  Title level inconsistent:

  Authors
  ~~~~~~~

In fact the Authors section is inside a Credits first level title, ====,
and should be a second level title, ----,
instead of a third level, ~~~.

[sbidoul]

Do you have an example where it failed?

[dreispt]

Yes:
Pull OCA/account-fiscal-rule#116
Then run oca-gen-addon-readme --repo-name=account-fiscal-rule --branch=13.0 --addon-dir=account_avatax

[sbidoul]

@dreispt I think it should work if you change the section underlines to tilde (~) in your fragments.
It has been a restriction since the beginning that this is the only allowed title underline in fragments.
It is mentioned in the example here, although admitedly it is not easily discoverable.

[dreispt]

Indeed those instructions could/should be in a better place. DESCRIPTION.rst sounds like the best place for it. Not finding them, I referred to the RST docs, and that led to this...

[dreispt]

@sbidoul Investigating further, subsections are possible. I added documentation for this in the main DESCRIPTION fragment, in #460