When a user invokes packer for a build or validation, the template being
processed needs components to be present for Packer to process it
without error.
If the component cannot be found from the plugins loaded (or from the
components bundled with Packer), Packer errors, and the command fails.
This is expected, but the error message does not suggest anything to fix
the error, potantially leaving users confused at the problem.
This commit suggests either a replacement (in case of a typo), or points
to the web documentation for Packer, specifically the integrations, so
they can look for the plugin they're missing, and install it, so
subsequent invocations of Packer work.