feat: Add dark and blue variants to the systray icon set and add the "TrayIconStyle" option in arch-update.conf

[hunabku94]

Description

Add the following style/color variants to the systray applet icon set:

• dark (Useful to make the systray applet icon more visible when using a light theme)
• blue (Matches the blue variant used by the official Arch Linux logo)

Add the TrayIconStyle option in the arch-update.conf configuration file to select which icon style/color variants to use (e.g. TrayIconStyle=dark).
Defaults to light.

Screenshots / Logs

Light (classic) variant:

Dark variant:

Blue variant:

Addressed feature request

Closes #240

[Antiz96]

Thanks a lot for your contribution!
That's a really nice addition 😄

[Antiz96]

With the changes added in this pull request, it should be relatively easy to add new additional style/color variants for the systray icon!

If anyone passing by is interested to contribute new style/color variants for the systray icon, you can open a pull request including the following changes:

1 - Copy the arch-update-light.svg & the arch-update_updates-available-light.svg files (which are under src/icons) and update the name suffix to match your new style/color variant (e.g. for a yellow variant: arch-update-yellow.svg & the arch-update_updates-available-yellow.svg).

2 - Modify the value of the fill: parameter with the hex color code that matches your new style/color variant in both files (do not update the value of the second fill: parameter in the arch-update_updates-available-*.svg file, as this is one is for the red circle that shows up when there are new available updates).

3 - Update the list of valid values for the TrayIconStyle option in the src/lib/config.sh file with your new style/color variant (e.g. for a yellow variant: [...](light|dark|blue|yellow)[...]).

That's it!
Once the changes are merged and released, everyone will be able to use your new style/color variant via the TrayIconStyle option in the arch-update.conf configuration file (e.g. for a yellow variant: TrayIconStyle=yellow). 🎨