API Change
1. Indicate `exp_name` field in config to output logs and files
Env(dizoo)
1. selfplay/league demo (12)
2. pybullet env (16)
3. minigrid env (13)
4. atari enduro config (11)
Algorithm
1. on policy PPO (9)
2. ACER algorithm (14)
Enhancement
1. polish experiment directory structure (10)
2. split doc to new repo (4)
Fix
1. atari env info action space bug
2. env manager retry wrapper raise exception info bug
3. dist entry disable-flask-log typo
Style
1. codestyle optimization by lgtm (7)
2. code/comment statistics badge
3. polish github CI workflow
**Contributors**: PaParaZz1 HansBug YinminZhang simonat2011