Merge pull request #10 from optuna/fix-pr-template

Fix PR template

.github/pull_request_template.md

@@ -1,12 +1,18 @@
 Please read the following and if you agree, please click the checkbox below.
 
 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.
 
-  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.
 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.
+
+## Motivation
+<!-- Describe your motivation why you will submit this PR. This is useful for reviewers to understand the context of PR. -->
+
+## Description of the changes
+<!-- Describe the changes in this PR. -->