fix: #381 [x] parcel -> parcel-bundler

[chr33s]

Summary

fixes #381, migrate from parcel to parcel-bundler and bump version to 6.0.0

Test plan

Tests should be unaffected.

[vercel]

This pull request is being automatically deployed with ZEIT Now (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://zeit.co/gregberge/svgr/qospfliqp
✅ Preview: https://svgr-git-fork-chr33s-master.gregberge.now.sh

[chr33s]

@gregberge as requested in #407

[codecov]

Codecov Report

Merging #410 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #410   +/-   ##
=======================================
  Coverage   85.63%   85.63%           
=======================================
  Files          30       30           
  Lines         522      522           
  Branches      143      143           
=======================================
  Hits          447      447           
  Misses         62       62           
  Partials       13       13

Impacted Files	Coverage Δ
packages/parcel-plugin-svgr/src/asset.js	100% <ø> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8b2129b...d1db283. Read the comment docs.