Clears up which versions of Node are supported

[peterramsing]

What kind of change is this? (Bug Fix, Feature...)
Doc Update

What is the current behavior (You can also link to an issue)
Poorly written (me)

What is the new behavior this introduces (if any)
It's clear. Thanks, @matchdav (see #426 )

Does this introduce any breaking changes?
No

Does the PR fulfill these requirements?

• [N/A] Tests for the changes have been added
• Docs have been added or updated

[codecov]

Codecov Report

Merging #427 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #427   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          19     19           
  Lines         701    701           
=====================================
  Hits          701    701

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