`mach node` and `mach npm` commands now available

[dmos...@mozilla.com]

`mach node` and `mach npm`

Many developers have multiple versions of NodeJS installed on their systems. Using different versions of `node` and `npm` on the same data can lead to weird and hard-to-diagnose errors.

For those developers who need to directly invoke the version of node used by the build system in the mozilla-central tree, it’s now possible to ensure that you’re using those versions by invoking them as `mach node …` and `mach npm …`.

For those interested, https://bugzilla.mozilla.org/show_bug.cgi?id=1652173 is where this work landed.