Mandatory import of sun.misc

[MrEasy]

Hi,
since version 3.20.0, the manifest contains a mandatory Import-Package declaration for package sun.misc.

This is problematic in OSGi environments not providing access to this package
and is unneeded from my point of view, since only usage is in org/jline/utils/Signals.
There it is accessed via reflection, so an optional import would be right from my point of view.

[MrEasy]

@mattirn Thanks for the fast change!