Make version.ts use a constant and create the file during the build process. (#818)

[dpvc]

This PR resolves the build issue that was reported with v3.2.1 due to the dynamic lookup of the version number by creating the version.ts file via components/bin/version, which is run during the travis-ci publish process (and can be run by hand at any point).

Resolve issue #818 and mathjax/MathJax#2880

[zorkow]

lgtm.

Since I've just seen the line: Do we know if travis works with stable again?

[dpvc]

Do we know if travis works with stable again?

Last time I found out by the fact that the publish run failed, and I tracked down the error message. Could always try that again. I will see if I can find something indicating the current state of affairs.

[dpvc]

The default OS used by Travis-CI is ubuntu 16.04, unless you request otherwise. It looks like node.js v18 changed the library version they use, and that ubuntu 16.04 doesn't have it, nor does 18.04; you need 18.10 or 20.04 to allow it to work. Travis-CI does have a 20.04 option, so I will switch to that and see if that allows the use of the stable version of node.js again.

[dpvc]

It looks like the update to 20.04 did the trick. Back to stable version of node.