adding pureblack

[Chris-McElroy]

i added a new theme, called pureblack
it's a very minimalist, all black theme
the css file and description can be found here
the css is included in the pr, and a screenshot for both this and the nordic theme are included in the gallery of the main readme file

[clins1994]

@Chris-McElroy thanks for making this. I want to make a pure black as well but a bit different

things i noticed in yours that i plan to change

• the chat background is still gray, want to make it black
• want to remove the chat fade black => transparent
• the space panel is still gray, want to make it black
• i dislike the font but no big deal, easy to change right if anyone wants to

then i want to make it minimalist and hide some unnecessary things like names in favorites (i know what profile pic my favorites use) ...

for the light version it would be just inverted colors and kind of very high contrast

would also be cool to have a soft version like https://github.com/antfu/vscode-theme-vitesse

[clins1994]

Standardize to 2 or 4 spaces here?

Suggested change

	--message-color-lightness: 100%;
	--reply-bg-saturation: 0%;
	--reply-bg-lightness: 10%;
	--sender-name-saturation: 0%;
	--sender-name-lightness: 100%;
	--add-reaction-saturation: 0%;
	--read-receipt-tooltip-fg: 100%;
	--message-color-lightness: 100%;
	--reply-bg-saturation: 0%;
	--reply-bg-lightness: 10%;
	--sender-name-saturation: 0%;
	--sender-name-lightness: 100%;
	--add-reaction-saturation: 0%;
	--read-receipt-tooltip-fg: 100%;

[clins1994]

Run prettier? ^^