Documentation + shutdown handling in examples

[brettmc]

• Reorganise and extend main README
• Ensure examples call shutdown on the tracer provider

[codecov]

Codecov Report

Merging #792 (04474e6) into main (e946dc7) will not change coverage.
The diff coverage is n/a.

❗ Current head 04474e6 differs from pull request most recent head e9b3c0b. Consider uploading reports for the commit e9b3c0b to get more accurate results

@@            Coverage Diff            @@
##               main     #792   +/-   ##
=========================================
  Coverage     79.52%   79.52%           
  Complexity     1405     1405           
=========================================
  Files           160      160           
  Lines          3468     3468           
=========================================
  Hits           2758     2758           
  Misses          710      710           

Flag	Coverage Δ
7.4	79.52% <ø> (ø)
8.0	79.59% <ø> (ø)
8.1	79.59% <ø> (ø)

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