Theme: add adwaita-light theme

[AbrA-K]

Fixes my Issue #10631.
The colors I used are from the adwaita-dark theme, not from the gtksourceview5 Adwaita theme, because I felt the colors had a better contrast to the background that way. These and other changes where mentioned in my issue (first post) - if you want a more direct analog to the dark theme, I could change this to be more in line with the original.

Lastly, I removed the line with the author of the dark theme. They didn't make adwaita-light, but It's HEAVILY based on that.

[brielov]

Can we get this merged?

[the-mikedavis]

Can this be done with theme inheritance instead? See gruvbox_light as an example: you can use inherits = "adwaita-dark" and then overwrite the colors in the palette and any styles that don't match adwaita-dark

[brielov]

@the-mikedavis I think @AbrA-K ended up not sharing colors with adwaita-dark but rather using other colors from gtksourceview which would make inheritance rather useless in this case, but I might be mistaken.

[AbrA-K]

No I've (mostly) copy&pasted the colors from adwaita-dark.

I'll change it to use inheritance once I have the time - which should be either later today or tomorrow.

[AbrA-K]

I'm using inheritance now + I saw that it was hard to see when you are in insert mode (the cursor was black in normal&insert mode) so I changed that to a yellow when in insert mode. I hope I didn't miss anything else.