vim: Add vim-astro

Although I haven't used it to its fullest potential,
https://astro.build/ seems interesting.

vim/.vimrc

@@ -50,6 +50,7 @@ call plug#begin('~/.vim/plugged')
     Plug 'dbeniamine/todo.txt-vim',     {'for': 'todo'}
     Plug 'lervag/vimtex',               {'for': 'tex'}
     Plug 'pantharshit00/vim-prisma',    {'for': 'prisma'}
+    Plug 'wuelnerdotexe/vim-astro',     {'for': 'astro', 'branch': 'main'}
     Plug 'isobit/vim-caddyfile'
 call plug#end()