feat: add sqlx-cli to shell.nix

.gitignore

@@ -2,3 +2,4 @@
 .DS_Store
 /.cache
 /node_modules
+testing.db

shell.nix

@@ -6,6 +6,8 @@ mkShell rec {
   nativeBuildInputs = [
     pkg-config
     openssl
+    # TODO: Figure out a better way to include sqlx only in dev shells (release shell?)
+    sqlx-cli
   ];
   buildInputs = additionalBuildInputs;
   LD_LIBRARY_PATH = lib.makeLibraryPath buildInputs;