Add \cvskill support to :PROPERTIES:

[gouvinb]

Proposal

Summary and problem statement

Currently "\cvskill" is supported through a latex block, like this:

* Language

#+BEGIN_EXPORT latex
\cvskill{English}{5.0}
#+END_EXPORT

The objective of this project being to make a CV in pure org format, "\cvskill must be supported in a more adapted format.

Motivation, use-cases, and solution sketches

There are 3 points to consider for this feature:

1. The skill level should be an entry in :PROPERTIES:.
2. The skill name should be a headline.

Design proposals

** English
:PROPERTIES:
:CV_ENV:      cvskill
:SKILL_LEVEL: 5.0
:END: