Auto-generate VISCtemplates website with pkgdown/GH actions

[slager]

Description

Draft PR for auto-generated VISCtemplates website. You can preview the built site locally from this branch with pkgdown::build_site().

Related Issues

#313
FredHutch/VISCfunctions#119

Checklist

• This PR includes unit tests
• This PR establishes a new function or updates parameters in an existing function
  • The roxygen skeleton for this function has been updated using devtools::document
• I have updated NEWS.md to describe the proposed changes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.41%. Comparing base (d0f23c7) to head (6c866ca).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #323   +/-   ##
========================================
  Coverage    85.41%   85.41%           
========================================
  Files           10       10           
  Lines          377      377           
========================================
  Hits           322      322           
  Misses          55       55           

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[kelliemac]

note: waiting on progress on #337 before merging this to develop