import release notes as written on GitHub in Markdown, for the
last release, prepending a first-level heading with the release
name, which for us equals the tag, only; we shall be using this
file to paste as future release notes, *and* we’ll be generating
the docs/versions.html file from it; this can be achieved by
using a subset of Markdown only

> 13887ef9 corrects a problem where synchronizer.js would block the users
> drawCallback when updating the zoom of connected charts.

some optimisations while here

using the website mentioned at scripts/generate-documentation.py
at the bottom which, however, nukes U+00A0, so temporarily escape
them!

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is most likely (part of) the #1011 cause

This reverts commit 3034672b.

This pull request fixes the broken zoom functionality (issue #611) and
console errors in the drawing demo. It simply adds the
willDestroyContextMyself attribute, and removes the now unimplemented
functions in the defaultInteractionModel. Comments have also been added
to explain to users why calls are missing.

> Hi, yep, the bug is still there. Select the zoom functionality in
> https://dygraphs.com/gallery/#g/drawing with the console open, and try
> a zoom, or move the mouse over the canvas.

(cherry picked from commit b773805f)

• drop huge sourcesContent, we just need the original source
  present when in-browser debugging…
• fix up relative paths to system components, which are in
  absolute /usr or so, by perlre(1), for repro-builds #1029670
• as a side effect, the bogus file key browserify generated also
  vanishes (now done for all browserify output)

(cherry picked from commit a575be0c)

hiding the 2.1.2 intermediate, as it was test-only