Improve .prettierignore file (#17632)

Co-authored-by: fisker <lionkay@gmail.com>

.prettierignore

@@ -1,6 +1,9 @@
 **/.yarn/*
 
+# Ignore directories and files in 'tests/format'
 /tests/format/**/*.*
+# Unignore directories and 'format.test.js' file
+!/tests/format/**/
 !/tests/format/**/format.test.js
 /tests/integration/cli/
 /tests/integration/plugins/**/*.*

tests/format/flow-repo/esproposal_decorators.ignore/format.test.js

@@ -1,5 +1,5 @@
 runFormatTest(import.meta, ["flow"], {
   errors: {
-    hermes:["test.js"],
+    hermes: ["test.js"],
   },
 });

tests/format/flow-repo/esproposal_decorators.warn/format.test.js

@@ -1,2 +1 @@
-runFormatTest(import.meta, ["flow"], {errors: { hermes: ["test.js"] }
+runFormatTest(import.meta, ["flow"], { errors: { hermes: ["test.js"] } });
-});