Release v1.5.3

### FIXED
- CI: release script affected by changing to setup-java@2.1.0

### Added
- Enable dependabot

### Removed
- Remove Plugin-Id property.

### Changed
- Drop configuration of jCenter
- Bump Gralde@6.9
- Bump Kotlin(JVM)@1.5.0
- Bump gradle-plugin-publish@0.14.0
- Bump dokka@1.4.32
- CI: Bump setup-java@2.1.0
- CI: Bump upload-artifact@2.2.3
- CI: Bump checkout@2.3.4

Signed-off-by: Hiroshi Miura <miurahr@linux.com>