themes/powerline: Added hex color capacity and user info text color

[GiulianoWF]

• Updated the set_color function to support parsing RGB and Hex color formats.
• Introduced the hex_to_rgb function for converting Hex to RGB color values.
• Modified the __powerline_left_segment function to accept the text color as third argument of each segment.
• Enhanced the __powerline_user_info_prompt function to pass the text color as its third argument.

[GiulianoWF]

Thanks for the feedback! I've updated the PR with the suggested changes.

Regarding the powerline-naked theme, I've added a new variable as per the discussion. It's currently not active due to the way the background color parameter is utilized.

[GiulianoWF]

I wanted to let you know that I've amended my last commit because I forgot to update a variable name. I wasn't entirely sure about the process and ended up force-pushing the change. I now understand this might not be the best practice, and I apologize for any mix-up it has caused.

If this is an issue, I'm more than willing to close this PR and open a new one with a fresh branch to keep things clean. Just let me know what works best for the project.

Thank you for your understanding.

[akinomyoga]

Don't worry about it.

Actually, force-pushing of organized commits is more welcome than trivial commits going back and forth. PRs with good quality would be developed by the discussions, where additional changes are typical. Meanwhile, for later investigations into the background of implementation details, it's good to have an organized history with each commit containing a related set of changes. It might depend on the project, but I prefer to finally have reorganized commits with rebasing/force-pushing/etc in PRs.

Anyway, this time, I'll probably squash all of the commits finally since this introduces a new theme. It's different from a PR containing multiple independent fixes to an existing one.

[akinomyoga]

Anyway, this time, I'll probably squash all of the commits finally since this introduces a new theme. It's different from a PR containing multiple independent fixes to an existing one.

Ah, sorry, this is not a new theme. I've mistaken it with another PR, #509, which tries to introduce the powerline-icon theme. This PR actually contains two independent features, the RGB color support and the specification of the user-info text color. However, these two changes are already mixed in the initial commit, so I wouldn't try to separate it into two commits, i.e., I'll squash them.

(If you would like, you can squash the commits and again split it into two for the RGB color and the user-info text color. In such a case, please force-push them to this PR rather than creating another PR, for the continuation of the discussion.)

[GiulianoWF]

Ok, done the changes.

[GiulianoWF]

And done

[akinomyoga]

I've merged the PR. Thank you!