breaking: replace shelljs w/ fs-extra where possible

[erisu]

Motivation, Context & Description

• Added fs-extra as release dependency
• Replace shelljs with fs-extra where possible.
• Remove shelljs as release dependency

Testing

• npm t

Checklist

• [x] I've run the tests to see all new and existing tests pass

[codecov-commenter]

Codecov Report

Merging #95 into master will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #95   +/-   ##
=======================================
  Coverage   93.54%   93.54%           
=======================================
  Files           2        2           
  Lines          31       31           
=======================================
  Hits           29       29           
  Misses          2        2           

Impacted Files	Coverage Δ
bin/lib/create.js	93.10% <100.00%> (ø)

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