contributing file translating (#350)

Author: yourSylvia

CONTRIBUTING.en.md

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+# Contributing
+
+## Translation
+
+Please pick any work without translation by `submit new issue`. English version and Chinese version are distinguished by file name, e.g. Chinese version file name abc.md, the corresponding English version should be abc.en.md. 
+
+Manual translation instead of machine translation, there is no need to translate the technical jargon.
+
+## Contributing to problems
+
+Please follow the template of "problems", what you need to submit are:
+
+- Problem and solution markdown file
+- Add the link of the solution in README.md
+- Add the link of the solution in README.en.md (optional)
+- draw.io file(xml) or pictures (optional)
+
+> Template for reference: [1014.best-sightseeing-pair](./templates/problems/1014.best-sightseeing-pair.md)
+> Online painting tools like https://excalidraw.com/, draw.io, processon or iPad apps
+
+## Contributing to daily problem
+
+- Please follow the template of "daily problem" and submit the issue with correct tags (can refer to official tags on LeetCode).