docs: align notation for change log file name pattern

also add a note that we are using English only for change log

Author: id

.github/pull_request_template.md

@@ -10,7 +10,7 @@ Please convert it to a draft if any of the following conditions are not met. Rev
 
 - [ ] Added tests for the changes
 - [ ] Changed lines covered in coverage report
-- [ ] Change log has been added to `changes/{ce,ee}/(feat|perf|fix)-<PR-id>.en.md` files
+- [ ] Change log has been added to `changes/(ce|ee)/(feat|perf|fix)-<PR-id>.en.md` files
 - [ ] For internal contributor: there is a jira ticket to track this change
 - [ ] If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
 - [ ] Schema changes are backward compatible

CONTRIBUTING.md

@@ -84,8 +84,9 @@ The footer should contain any information about **Breaking Changes** and is also
 
 Changes affecting EMQX functionality shall be described in a separate markdown file under `changes` directory.
 
-File name pattern: `changes/{ce,ee}/(feat|perf|fix)-<PR-id>.en.md`, where:
+File name pattern: `changes/(ce|ee)/(feat|perf|fix)-<PR-id>.en.md`, where:
 
 - `ce,ee`: Indicates whether given change affects community and enterprise edition (`ce`), or enterprise edition only (`ee`); for any change only one file is needed as enterprise edition absorbs all changes from the community edition automatically. When in doubts, one could consult [documentation](https://www.emqx.io/docs/en/latest/). Enterprise features have a corresponding "Tip" banner, see for example [here](https://www.emqx.io/docs/en/v5.1/data-integration/data-bridge-influxdb.html).
 - `feat|perf|fix`: Whether the change is a new functionality (`feat`), performance improvement (`perf`), or a bug fix (`fix`).
 - `PR-id`: Github pull request id. Since pull request id cannot be known before the PR is actually created, it's common to add change log entry in a separate commit.
+- `en`: ISO 639-1 language code indicating the language the change log entry is written in. Right now we are only accepting entries in English.