misc webpack tweaks

[silverwind]

• reduce verbosity during build
• use array form use to allow easier extension
• disable uninteresting source maps
• disable symlink resolution for a speedup

Overall this gives about 10% speedup on the webpack build.

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@43c2ba0). Click here to learn what that means.
The diff coverage is 23.43%.

@@            Coverage Diff            @@
##             master    #9924   +/-   ##
=========================================
  Coverage          ?   42.28%           
=========================================
  Files             ?      608           
  Lines             ?    79392           
  Branches          ?        0           
=========================================
  Hits              ?    33570           
  Misses            ?    41679           
  Partials          ?     4143

Impacted Files	Coverage Δ
services/pull/commit_status.go	5.19% <0%> (ø)
routers/repo/pull.go	28.67% <0%> (ø)
models/commit_status.go	64.13% <100%> (ø)
routers/api/v1/repo/status.go	44.57% <50%> (ø)
modules/structs/commit_status.go	54.54% <54.54%> (ø)

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