v6.21.0

• resolved issues #357 #457 #376 #488 #489
• replaced request with got
• update diedriver version to 3.150.1
• updated chromiumedge version to 87.0.637.0
• updated geckodriver version to 87.0.637.0
• decreased package size by 60% (8.6Mb)
• nodejs version in docker updated to 12
• added eslint + prettier
• minor bug fixes