flake: Add rust-analyzer

flake.nix

@@ -24,7 +24,13 @@
       {
         devShells = {
           default = pkgs.mkShell {
-            buildInputs = [ rust nodejs pkgs.cargo-leptos pkgs.dart-sass ];
+            buildInputs = [
+              rust
+              nodejs
+              pkgs.cargo-leptos
+              pkgs.dart-sass
+              pkgs.rust-analyzer
+            ];
           };
         };
       });