plugin text syntaxes: remove side effect on init: When text syntaxes was initialised, `syntaxes` dict was filled, but it was a class attribute. As a result, re-initialising it (which may happen for tests, and maybe in the future dynamically), was not starting with an empty dict, but with an already-filled one, resulting in conflicts. This patch fixes it by moving `syntaxes` to an instance attribute.

.. _contribuing:

===========
contribuing
===========

This part of the documentation is for people willing to contribute to the development of
Libervia and its ecosystem, it is not needed to read this if you only plan to use the
software.

.. toctree::
   :glob:
   :maxdepth: 2

   testing