Documentation site update

[abhro]

• Use Documenter.jl v1
• Clean installation instructions
• Add headers for docstrings
• Use Downloads.download instead of Base.download
• Add cross-reference links

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.71%. Comparing base (97bdfc9) to head (f0be08c).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #393 +/- ## ======================================= Coverage 91.71% 91.71% ======================================= Files 10 10 Lines 712 712 ======================================= Hits 653 653 Misses 59 59 ```

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[abhro]

The failed action for Documenter is also happening on other PRs on this repo

[nhz2]

Thank you for fixing this up