renamed changed lsp names and use web-devicons as a full plugin (#49)

fix #48 

- Renamed LSP servers as they were changed upstream.
- Enable web-devicons as a nixvim plugin instead of installing them as a
extra package.

config/default.nix

@@ -51,5 +51,6 @@ _: {
     ./plugins/utils/markdown-preview.nix
     ./plugins/utils/obsidian.nix
     ./plugins/utils/toggleterm.nix
+    ./plugins/utils/web-devicons.nix
   ];
 }