update contribution guide

docs/CONTRIBUTING.en.md

@@ -0,0 +1,19 @@
+# Contribution guide
+
+## Creating a PR
+Thank you for your PR! Before creating a PR, please check the following:
+- If possible, prefix the title with a keyword that identifies the type of this PR, as shown below.
+  - fix / refactor / feat / enhance / perf / chore etc.
+  - Also, make sure that the granularity of this PR is appropriate. Please do not include more than one type of change or interest in a single PR.
+- If there is an Issue which will be resolved by this PR, please include a reference to the Issue in the text.
+- Please add the summary of the changes to CHANGELOG.md. However, this is not necessary for changes that do not affect the users, such as refactoring.
+- Check if there are any documents that need to be created or updated due to this change.
+- If you have added a feature or fixed a bug, please add a test case if possible.
+- Please make sure that tests and Lint are passed in advance.
+  - You can run it with `npm run test` and `npm run lint`.
+- Run `npm run api` to update the API report and commit it if there are any diffs.
+Thanks for your cooperation 🤗
+
+**ℹ️ Important:** If your language is not Japanese, you do not need to translate and write the description in Japanese.
+The accuracy of translation into Japanese is not high, so it will be easier for us to understand if you write it in the original language.
+It will also allow the reader to use the translation tool of their preference if necessary.