Add code of conduct

.github/pull_request_template.md

@@ -1,15 +1,8 @@
-Please read the following and if you agree, please click the checkbox below.
+## Contributor Agreements
 
-1. By making a contribution to this project, I certify that:
-    a. The contribution was created in whole or in part by me and I have the right to submit it under the MIT license indicated in the file; or
-    b. The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open-source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the MIT license, as indicated in the file; or
-    c. The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it.
+Please read the CODE_OF_CONDUCT.md and if you agree, please click the checkbox below.
 
-2. By making a contribution to this project, I agree that the MIT license applies to the contribution and the contribution is used by other people under the MIT license.
-
-- [ ] I agree to the above conditions.
-
-Please read the [tutorial guide](TBD) to register your implemented algorithm in OptunaHub.
+- [ ] I agree to the code of conduct.
 
 ## Motivation
 <!-- Describe your motivation why you will submit this PR. This is useful for reviewers to understand the context of PR. -->

CODE_OF_CONDUCT.md

@@ -0,0 +1,13 @@
+1. By making a contribution to this project, I certify that:
+
+(a) The contribution was created in whole or in part by me and I have the right to submit it under the MIT license indicated in the file:
+
+(b) The contribution is based upon previous work that, to the best of my knowledge, is covered under an appropriate open-source license and I have the right under that license to submit that work with modifications, whether created in whole or in part by me, under the MIT license, as indicated in the file; or
+
+(c) The contribution was provided directly to me by some other person who certified (a), (b) or (c) and I have not modified it.
+
+2. By making a contribution to this project, I agree that the MIT license applies to the contribution and the contribution is used by Preferred Networks (“PFN”) or third party under the MIT license.
+
+3. I agree that PFN may remove my contribution from the Optuna Hub at any time, if the Contribution likely violates any of applicable law and regulation, or likely infringe or misappropriate any rights of any person or entity. I ALSO AGREE THAT PFN SHALL NOT BE RESPONSIBLE OR LIABLE FOR SUCH REMOVAL OF MY CONTRIBUTION.
+
+4. I AGREE THAT PFN SHALL NOT BE RESPONSIBLE OR LIABLE FOR USE MODIFICATION OR REMOVAL OF MY CONTRIBUTION BY THIRD PARTY.