give weight to merged PR types

this might be controversial, but we could have introduce weight to calculate the points for the PRs:

- docs: 1x
- chore: 1x
- style: 1x
- build: 2x
- ci: 2x
- refactor: 2x
- test: 2x
- perf: 3x
- fix: 3x
- feat: 3x

While everything is important, I think it makes the system a little more fun and rewarding.