Prepare for the 2.0 release

[jmwright]

This addresses #315 and goes with this draft release.

@adam-urbanczyk Please take a look to see if I've missed anything.

[codecov]

Codecov Report

Merging #325 into master will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #325   +/-   ##
=======================================
  Coverage   95.38%   95.38%           
=======================================
  Files          19       19           
  Lines        4707     4707           
=======================================
  Hits         4490     4490           
  Misses        217      217           

Impacted Files	Coverage Δ
cadquery/__init__.py	100.00% <100.00%> (ø)

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[adam-urbanczyk]

Looks good but I'll have another pass. Two missing things I spotted:

1. Text support
2. Add section about deprecations and breaking changes (e.g. upcoming workplane center option change).

[adam-urbanczyk]

I added few things. Feel free to change the wording (my English might be sloppy).

[jmwright]

@adam-urbanczyk Thanks. I fixed one additional typo. Once all the checks pass I'll merge this, create the git tag, then finish/publish the release.

[adam-urbanczyk]

Thanks @jmwright !