Add Slack handles to MAINTAINERS
-In alphabetical order:
+The maintainers are generally available in Slack at
+https://weave-community.slack.com/messages/flux/ (obtain an invitation
+at https://slack.weave.works/).
-Hidde Beydals (github: @hiddeco)
-Justin Barrick (github: @justinbarrick)
-Michael Bridgen (github: @squaremo)
-Nick Cabatoff (github: @ncabatoff)
+In alphabetical order:
+Hidde Beydals (github: @hiddeco, slack: hidde)
+Justin Barrick (github: @justinbarrick, slack: Justin Barrick)
+Michael Bridgen (github: @squaremo, slack: mbridgen)
+Nick Cabatoff (github: @ncabatoff, slack: Nick Cabatoff)
