Implement a global Color Picker

[isneezy]

Summary / How this PR fixes the problem?

Implement a global Color Picker ported from this awesome little tool https://github.com/RonnyDo/ColorPicker

Steps to Test

1. Draw a and select a shape
2. Click on the first delete icon from the left to right of the Fills panel
3. Pick a color

Screenshots

Known Issues / Things To Do

• When used on multi-monitor setup the application window should be on the primary monitor otherwise it won't pick colors from other monitors
• Wayland compatibility, mentioned by @bilelmoussaoui here

This PR fixes/implements the following bugs/features:

• Related to Beta Release Wishlist #358

[bilelmoussaoui]

The current implementation won't work under wayland. The proper solution would be using the xdg portals to pick the color and fallback to this in case the dbus interface is not available. See https://flatpak.github.io/xdg-desktop-portal/portal-docs.html#gdbus-method-org-freedesktop-portal-Screenshot.PickColor

The XDG portals are not Flatpak specific, they are just a bunch of dbus interfaces (as a specification) that have to be implemented by the desktop environment, there are two implementation currently, kde & gtk which should cover most use cases.

[isneezy]

@bilelmoussaoui thanks for your quick feedback. I'll first finish up this implementation and get it working and then I'll move forward into the XDG implementation as you suggested. I'm new to vala and Linux programming so in the meantime, I'll ping you for help.

[bilelmoussaoui]

Sure, no problem :) thanks for the contribution! let us know if we can help somehow & good luck in your journey.

[isneezy]

@bilelmoussaoui thanks. Do you know the name or how I can get the eyedropper icon? I Can't find any.

[Alecaddd]

@bilelmoussaoui thanks. Do you know the name or how I can get the eyedropper icon? I Can't find any.

The elementary icon theme doesn't currently have a symbolic color picker.
I will create a dedicated icon for it. For now don't worry about it and you can temporarily use the preferences-color-symbolic.

Thank you so much for your contributions, you're helping us a lot!

[Alecaddd]

Just a few changes on your awesome contribution.

[Alecaddd]

Here's a bunch of fixes and improvements.