Additional KiCad documentation and presentations.

Since this documentation package has a separate release time-line,
you may have to specify the version of the installed KiCad package if
it is newer than this documentation package.  At the time of writing,
it was "7.0.2". To specify another release, run this SlackBuild
as follows:

  # KICAD_VERSION="7.0.5" ./kicad-doc.SlackBuild
documentation is available in a number of different languages. see
CMakeLists.txt for a full list. this build will default to en
(english) but can be changed by setting the environment variable
DOCLANG before running the script. for example, for french, use

  # DOCLANG=fr ./kicad-doc.SlackBuild

for more than one language, use a quoted semicolon separated list. eg

  # DOCLANG="en;fr;de;it;jp;cz" ./kicad-doc.SlackBuild

note: once package is created, node.js is no longer required
(build dep only)