feat: add perttier to format the markdown files

Author: ryan4yin

.github/CONTRIBUTING.md

@@ -46,10 +46,13 @@ Boot up the documentation site locally, with live reloading of the source code:
 $ pnpm run docs:dev
 ```
 
-If you made a lot of changes, run the following command to check for typos before submitting a pull request:
+If you made a lot of changes, run the following command to check for typos & format the docs before submitting a pull request:
+
+> Generally, `nix develop` will add a pre-commit hook to run the following command before you commit.
 
 ```sh
 $ typos -w
+$ prettier --write .
 ```
 
 After executing the above command, visit <http://localhost:5173> and try modifying the source code. You'll get live update.

flake.nix

@@ -19,6 +19,7 @@
           nodejs = super.nodejs_20;
           pnpm = super.nodePackages.pnpm;
           yarn = super.yarn.override {inherit nodejs;};
+          prettier = super.nodePackages.prettier;
         })
       ];
       pkgs = import nixpkgs {inherit overlays system;};
@@ -28,6 +29,7 @@
         nodejs
         pnpm
         yarn
+        prettier
 
         git
         typos
@@ -40,12 +42,16 @@
           hooks = {
             typos.enable = true; # Source code spell checker
             alejandra.enable = true; # Nix linter
+            prettier.enable = true; # Markdown & TS formatter
           };
           settings = {
             typos = {
               write = true; # Automatically fix typos
               ignored-words = [];
             };
+            prettier = {
+              write = true; # Automatically format files
+            };
           };
         };
       };