chore: reflect actual policy about Committers' rights

CONTRIBUTING.md

@@ -20,13 +20,27 @@ Before creating an issue, please check the following:
 > **Warning**
 > Do not close issues that are about to be resolved. It should remain open until a commit that actually resolves it is merged.
 
-## Before implementation
+
+### Recommended discussing before implementation
+We welcome your purposal.
+
 When you want to add a feature or fix a bug, **first have the design and policy reviewed in an Issue** (if it is not there, please make one). Without this step, there is a high possibility that the PR will not be merged even if it is implemented.
 
 At this point, you also need to clarify the goals of the PR you will create, and make sure that the other members of the team are aware of them.
 PRs that do not have a clear set of do's and don'ts tend to be bloated and difficult to review.
 
-Also, when you start implementation, assign yourself to the Issue (if you cannot do it yourself, ask another member to assign you). By expressing your intention to work the Issue, you can prevent conflicts in the work.
+Also, when you start implementation, assign yourself to the Issue (if you cannot do it yourself, ask Commiter to assign you). By expressing your intention to work the Issue, you can prevent conflicts in the work.
+
+To the Commiters: you should not assign someone on it before the Final Desicion.
+
+### How issues are triaged
+
+The Commiters may:
+* close issue that is not reproducible on latest stable release,
+* merge issue into another issue,
+* or split issue into multiple ones
+
+@syuilo reserves Final Desicion rights including whether the project will implement feature and how to implement, but not always exercised.
 
 ## Well-known branches
 - **`master`** branch is tracking the latest release and used for production purposes.
@@ -39,7 +53,7 @@ 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.
+- If there is an Issue which will be resolved by this PR, please tie issues in the text.
 - Please add the summary of the changes to [`CHANGELOG.md`](/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.