Return '0' if cell is '0', empty otherwise

[steppicrew]

Distinguish between empty cells and cells containing '0'

[jholster]

Is the library anymore maintained? The first pull request for this bug was sent more than a year ago ("Fix when row[key] == 0"). Neither that or this pull request has been merged.

[steppicrew]

I think you're right: it seems not to be maintained anymore.
But the patched module works for us so we thought we'd add a pull request. Afterwards we realized that there already was one addressing the same problem, but I think our is slightly better so we let you chose which to merge... ;-)

[jholster]

@steppicrew I forked your fork, made minor modifications so that it installs with yarn, and published it as xlsx-writestream2.