feat: add fallback icon to context

[JB1905]

Closes #58

[codecov]

Codecov Report

Merging #59 (91ae412) into main (4516818) will not change coverage.
The diff coverage is 83.33%.

@@           Coverage Diff           @@
##             main      #59   +/-   ##
=======================================
  Coverage   97.61%   97.61%           
=======================================
  Files           4        4           
  Lines          42       42           
  Branches       16       17    +1     
=======================================
  Hits           41       41           
  Misses          1        1           

Impacted Files	Coverage Δ
src/context.tsx	75.00% <50.00%> (ø)
src/components/Icon.tsx	100.00% <100.00%> (ø)

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