Small tweaks to base.config to speed up dev watch times

[matt-gadd]

Type: feature

The following has been addressed in the PR:

• There is a related issue
• All code has been formatted with prettier
• Unit or Functional tests are included in the PR

Description:
Both the banner and the wrapper plugin both have to write to the entire chunk and cost significant time during building. Move the banner plugin to dist only, given it's not important in dev. Only enable the wrapper plugin (which is for AMD support) if using externals or in one of the test modes.

Sample build time with dev and watch:

before:

General output time took 4.78 secs

after:

General output time took 2.14 secs

[codecov]

Codecov Report

Merging #200 into master will decrease coverage by 0.28%.
The diff coverage is 20%.

@@            Coverage Diff             @@
##           master     #200      +/-   ##
==========================================
- Coverage   53.54%   53.26%   -0.29%     
==========================================
  Files          10       10              
  Lines         564      567       +3     
  Branches      134      137       +3     
==========================================
  Hits          302      302              
- Misses        262      265       +3

Impacted Files	Coverage Δ
src/base.config.ts	23.37% <0%> (-0.97%)	⬇️
src/dist.config.ts	32.2% <100%> (+1.16%)	⬆️

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