Merge branch 'js/trace2-doc-fixes'

Trace2 documentation updates.

* js/trace2-doc-fixes:
  trace2 docs: add missing full stop
  trace2 docs: clarify what `varargs` is all about
  trace2 docs: fix a JSON formatted example
  trace2 docs: surround more terms in backticks
  trace2 docs: "printf" is not an English word
  trace2 docs: a couple of grammar fixes