CODEOWNERS settings

The syntax for plugin settings is

CODEOWNERS.<setting> <value>

The following settings are currently supported:

Restrict code owners functionality for a certain destination branch. This CODEOWNERS file is then only active for pull requests with matching destination branch. Supported pattern format.
```
CODEOWNERS.destination_branch_pattern <branchpattern>
```
To exclude code owners functionality for pull requests with certain source branches, This CODEOWNERS file is then inactive for pull requests with matching source branch. Supported pattern format.
```
CODEOWNERS.source_branch_exclusion_pattern <branchpattern>
```
Enable subdirectories overrides, where a CODEOWNERS file in a subdirectory overrides all settings. Ideal when you have independent projects in subdirectories which require independent rules. By default, this is disabled and only the CODEOWNERS at the top of the repository is used.
```
CODEOWNERS.toplevel.subdirectory_overrides enable
```
Suppress info comment on pull request creation about added code owners. Comments are enabled by default.
```
CODEOWNERS.toplevel.create_pull_request_comment disable
```
Require reapproval from code owners for new changes in a pull request. Similar to Atlassian's Auto Unapprove app, but unapproves only reviewers that are code owners of the new changes. Auto unapproving is disabled by default.
```
CODEOWNERS.toplevel.auto_unapprove_on_change enable
```