Update Viridian for v1.0 support

[WYVERN2742]

In the v1.0 update for obsidian there are many breaking changes for themes. Currently, viridian is a legacy theme and cannot be installed untill it's updated.

There is a guide for migrating themes to v1.0

Viridian is a great theme that I use all the time, it would be lovely to keep using it!

[mulfok]

Thanks for leaving an issue here, I'll try my best to get it to work with v1.0. There are some additional things that I'd like to try and fix with the release for v1.0, so if I'll see if I can get it working today.

(thanks for using my theme!)

[josephdong1000]

+1, I absolutely love your theme and a 1.0 update would make my month :DDDD

[oyes77]

I tried installing it with BRAT but wasn't able to, is this the reason?