Update documentation

[VictorKoenders]

Addresses a lot of the items in #436

[codecov-commenter]

Codecov Report

Merging #480 (d78a2a5) into trunk (447c4c7) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##            trunk     #480   +/-   ##
=======================================
  Coverage   66.44%   66.44%           
=======================================
  Files          38       38           
  Lines        2691     2691           
=======================================
  Hits         1788     1788           
  Misses        903      903           

Impacted Files	Coverage Δ
derive/src/derive_enum.rs	0.00% <0.00%> (ø)
derive/src/derive_struct.rs	0.00% <0.00%> (ø)
src/config.rs	80.95% <ø> (ø)
src/de/mod.rs	65.51% <ø> (ø)
src/enc/mod.rs	60.00% <ø> (ø)

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