Feature: add line numbers to section

[aravindballa]

This PR has the changes required for adding line-numbers to the Section Options.

http://officeopenxml.com/WPsectionLineNumbering.php

[dolanmiu]

Could you add an example on how to use this feature?

[aravindballa]

I just added an example in ./demo/demo40.ts. Here is the output of it.

[knowtheory]

fwiw, i could totally use this on a project i'm working on right now :)

[dolanmiu]

If the author doesn't fix the build, i will fix it, make sure it passes and then merge

[codecov-io]

Codecov Report

Merging #262 into master will increase coverage by 1.4%.
The diff coverage is 73.33%.

@@            Coverage Diff            @@
##           master     #262     +/-   ##
=========================================
+ Coverage   89.56%   90.97%   +1.4%     
=========================================
  Files         242      250      +8     
  Lines        2846     2869     +23     
  Branches      156       69     -87     
=========================================
+ Hits         2549     2610     +61     
+ Misses        257      241     -16     
+ Partials       40       18     -22

Impacted Files	Coverage Δ
...ument/body/section-properties/line-number/index.ts	100% <100%> (ø)
src/file/document/body/section-properties/index.ts	100% <100%> (ø)	⬆️
...ment/body/section-properties/section-properties.ts	96.22% <66.66%> (-0.39%)	⬇️
...body/section-properties/line-number/line-number.ts	70% <70%> (ø)
src/file/table/table-properties/table-width.ts	85.71% <0%> (-14.29%)	⬇️
src/file/table/table-cell/table-cell-properties.ts	90.9% <0%> (-9.1%)	⬇️
...rc/file/table/table-properties/table-properties.ts	91.66% <0%> (-8.34%)	⬇️
src/file/paragraph/links/hyperlink.ts	92.3% <0%> (-7.7%)	⬇️
...c/file/table/table-properties/table-cell-margin.ts	78.26% <0%> (-1.74%)	⬇️
src/file/table/table-cell/table-cell.ts	71.42% <0%> (-1.65%)	⬇️
... and 50 more

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[dolanmiu]

Thanks! merged

will release a new rc soon

[dolanmiu]

Done here:

https://github.com/dolanmiu/docx/releases/tag/5.0.0-rc3