fish_title: add setting to configure pwd dir length

[ovv]

Add new pure_title_dir_length setting (default to 0) to configure the pwd dir length. 0 means complete directory name.

example with path '/foo/example/bar':

• pure_title_dir_length=0 -> '/foo/example/bar'
• pure_title_dir_length=1 -> '/f/e/bar'
• pure_title_dir_length=2 -> '/fo/ex/bar'

[ovv]

@edouard-lopez updated

[edouard-lopez]

Hello @ovv, Could you rebase your branch master and document your feature so we can merge it?

• [ ] update the README.md with feature documentation
• [ ] update the README.md with Features' list
• [ ] ~follow the release steps related to pure_version~

[ovv]

SHould be good to go. Let me know if more documentation is needed