Base+LibJS+LibWeb: Make prettier clean

Also use "// prettier-ignore" comments where necessary rather than
excluding whole files (via .prettierignore).

Libraries/LibJS/Tests/strict-mode-errors.js

@@ -7,6 +7,9 @@ test("basic functionality", () => {
         }).toThrowWithMessage(TypeError, "Cannot assign property foo to primitive value");
         expect(() => {
             primitive[Symbol.hasInstance] = 123;
-        }).toThrowWithMessage(TypeError, "Cannot assign property Symbol(Symbol.hasInstance) to primitive value");
+        }).toThrowWithMessage(
+            TypeError,
+            "Cannot assign property Symbol(Symbol.hasInstance) to primitive value"
+        );
     });
 });