Release OfflinPlugin v9:0.8.0

[Chaoba]

Release OfflinPlugin v9:0.8.0

Changelog mapbox-android-plugin-offline-v9:0.8.0:

Bugs

• Fix download notification doesn't dismiss issue. #1176

Release checklist

• [x] Cut the release branch
• [x] Run through testapp/demo app and test all activities
• [x] Update CHANGELOG.md
• [ ] Change version name to X.X.X in gradle.properties
• [ ] Change release branch in the circle.yml release job to the current branch
• [ ] Publish X.X.X artifact to Maven Central
• [ ] Change version name back to X.X.X-SNAPSHOT
• [ ] Change release branch in the circle.yml back to master
• [x] Merge the release branch to master
• [x] Tag version {artifact_name}-v{major_maps_sdk_version}:{plugin_version} in GitHub

Post-release

• [ ] Update README.md
• [x] Update constants.js file in android-docs repo
• [x] Generate updated javadocs and add to android-docs repo

/cc: @mapbox/android