Add featuretools_sql documentation

[sbadithe]

• Fixes Integration with SQL? #248
• This PR adds a guide in the docs/sources/guides folder that describes how to use featuretools_sql with featuretools
• It updates install.md to reflect the options users have for downloading featuretools_sql. The conda section is unchanged intentionally as we have not yet released featuretools_sql on conda
• An install test is added to install_test.yaml to check that users can install the add-on
• A doc is added to the guides section explaining how the user can set up the sql add-on
• Update the pyproject.toml file to reflect new doc requirements and new complete installation requirements

[codecov]

Codecov Report

Merging #2262 (27ad8ee) into main (e3f2f86) will not change coverage.
The diff coverage is n/a.

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##             main    #2262   +/-   ##
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  Coverage   99.32%   99.32%           
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  Files         148      148           
  Lines       17706    17706           
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  Hits        17586    17586           
  Misses        120      120           

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[gsheni]

Are we going to need a database instance running now for the docs? Can we use a mock instance instead?

[sbadithe]

Are we going to need a database instance running now for the docs? Can we use a mock instance instead?

Just record keeping here: as per discussion in meeting, went with code blocks instead