Geographic types documentation

[micahtyong]

Overview

In this PR, we provide concise documentation for #253, geographic data types.

Changes

• New documentation page, source/advanced/map.rst
• Citing geographic tutorial in FAQ.rst
• Adding as new tab in index.rst

Example Output

After running make html in the doc/ folder then opening the documentation to the new page, we should see the following (subject to change):

[codecov]

Codecov Report

Merging #358 (2684a14) into master (939799f) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #358   +/-   ##
=======================================
  Coverage   84.29%   84.29%           
=======================================
  Files          51       51           
  Lines        3884     3884           
=======================================
  Hits         3274     3274           
  Misses        610      610           

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[dorisjlee]

Thanks @micahtyong, I made some writing changes, but otherwise everything looks good!