Change type of revision to a number

[rowanc1]

I just worked through a bug that I didn't realize that revision in document properties had to be a number. I have changed the TypeScript to only allow numbers, which I think is clearer. This made the word doc angry when it was opened if there is arbitrary string in there.

The code change is backwards compatible as we cast this to a string before writing to XML. However, this will require people to unquote their revision numbers if they are using typescript.

[codecov-commenter]

Codecov Report

Merging #1217 (47099d0) into master (abbd620) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1217   +/-   ##
=======================================
  Coverage   99.30%   99.30%           
=======================================
  Files         314      314           
  Lines        3600     3600           
  Branches      454      454           
=======================================
  Hits         3575     3575           
  Misses         24       24           
  Partials        1        1           

Impacted Files	Coverage Δ
src/file/core-properties/properties.ts	100.00% <100.00%> (ø)
src/file/file.ts	90.15% <100.00%> (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 abbd620...47099d0. Read the comment docs.

[rowanc1]

There could be another check in here to ensure that options.revision >= 0, negative numbers in there also complain.