Update to howdoi 2.0.20

2.0.20

• Update dependency versions
• Add support for Python 3.10

2.0.19

• Fix typo

2.0.18

• Fixed issue with howdoi cache where cache misses would be printed to the console

2.0.17

• New documentation and mkdocs
• Fixed issue with how howdoi chooses the proper search engine (command line flags now override environment variables)
• Added a search engine fallback if one of the search engines fails