This is useful for plugins like dotbot-if [1] that want to instantiate
their own Dispatcher. Previously, the Dispatcher found the set of
available plugins on its own, but as of
b5499c7dc5, this was changed so that
plugins are passed in.
Given that it has been over two years since this behavior has been
broken/changed, reverting to the previous behavior of having the
Dispatcher auto-load plugins might not be ideal, which is why this patch
instead makes the set of plugins available via the Context for plugins
to use.
This was reported in the Dotbot repository [2], and earlier in dotbot-if
[3]. dotbot-if is currently using a workaround [4] that was originally
implemented in dotbot-ifplatform [5].
[1]: https://github.com/wonderbeyond/dotbot-if
[2]: https://github.com/anishathalye/dotbot/issues/339
[3]: https://github.com/wonderbeyond/dotbot-if/issues/1
[4]: https://github.com/wonderbeyond/dotbot-if/pull/2
[5]: e35b5c0d71
