Fix zsh theme install instructions

[fhoekstra]

As per the discussion and solutions provided around here:
dracula/zsh#11 (comment)

I figured I would add this to the site. The instructions for manual install and git install as they are on https://draculatheme.com/zsh right now don't work for me and other users. This works and is confirmed by multiple users.

I was not able to build the site locally yet, so please be careful with merging this until it's confirmed to work.

[luxonauta]

Hi 👋🏻, the instruction pages are generated based on API/installs in build-time, so when we deploy the site again, they are updated automatically. So when you need to update some instructions, you can tag me in the Issue; I will close this one, and soon we will redeploy the website.

[fhoekstra]

Thanks for your reply! I finally found the install instructions, stupid that I overlooked them in the theme-specific repo initially.
Like this?
dracula/zsh#52
I will tag you when it's merged