tools: add bash completion and update fish completion

[desertstsung]

Major changes:

1. initialize a (local-tested) bash completion file, also mentioned in Bash completions #315. Should we also consider about informing the packagers when the next version release? or clearify this in the changelog. IDK
2. update fish completion based the previous updated zsh comepletion.

Minor change:

1. add noise option into dither arguments list, both in zsh and fish completion.

[hpjansson]

Thanks, this is great. It's only missing the installation target in tools/completions/Makefile.am for bash. It should probably go to $(PREFIX)/bash-completion/completions/chafa.

(I just realized the target prefix is hardcoded to /usr/share, which is wrong. It should be set to ${datadir}, but that's for a different bug).

[desertstsung]

It's only missing the installation target in tools/completions/Makefile.am for bash.

Ah yes of course, it is so obvious in the folder! I didn't even open it for a look. OK, I'll do this later.

It should be set to ${datadir}

I don't have much exp on that, but after a search, I think it is worth to do and I can give a fix along with this PR :)

[hpjansson]

Looks good now. Thanks!