fix(frontend): workaround for @speckle/viewer not found error when running dev server

[fabis94]

workaround for the following issue: TypeStrong/fork-ts-checker-webpack-plugin#771

essentially we no longer clean the dist folder between @speckle/viewer rebuilds, so that fork-ts-checker-webpack-plugin doesn't break and think the types no longer exist

this does make the viewer package build process a few seconds longer, but there's no other option

[codecov]

Codecov Report

Merging #892 (d5034cb) into main (a0fe0b8) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #892   +/-   ##
=======================================
  Coverage   90.54%   90.54%           
=======================================
  Files          87       87           
  Lines        3374     3374           
  Branches        5        5           
=======================================
  Hits         3055     3055           
  Misses        319      319           

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