When working on the Documentation or when translating it, I often have to rebuild the doc locally to see the changes I made and see how it looks.

However, with the current configuration, It takes (on my computer at least) more than 4 minutes to build.

After investigating, I've found out that the build options on the Makefile of python-docs-fr and of cpython/Docs both have the `E` and `a` options set, which forces a complete rebuild, even when running locally.

https://github.com/python/cpython/blob/9ee1d42f019ac827f73479ce241e95733d050e67/Doc/Makefile#L178-L208
https://github.com/python/python-docs-fr/commit/af8c7a95ab5bc50523ba919c74bb6e6b89d16962

My proposal is to add a `make dev` in the `python-docs-fr` Makefile and add in `cpython/Docs` a mode which will only recompile the needed files.