Add MBS UI, PDC and mdapi to the application index

modules/ROOT/pages/services.adoc

@@ -139,6 +139,9 @@ Koji is the software that builds RPM packages for the Fedora project. It uses
 Mock to create chroot environments to perform builds that are both safe and
 trusted.
 
+MBS UI https://release-engineering.github.io/mbs-ui/[re.github.ui/mbs-ui]::
+Web interface atop the Fedora Module Build Service.
+
 Packages https://apps.fedoraproject.org/packages/[apps.fp.o/packages]::
 A meta-app over the other packaging apps; the best place to find out what is in
 the Fedora repositories. Which packages are present in which version, who is
@@ -195,6 +198,9 @@ it to dig into the history of the http://fedmsg.com[fedmsg] message bus. You
 can grab events by username, by package, by message source, by topic... you
 name it.
 
+mdapi https://mdapi.fedoraproject.org/[mdapi.fp.o]::
+Small API exposing the metadata contained in different RPM repositories.
+
 MirrorManager https://admin.fedoraproject.org/mirrormanager/[admin.fp.o/mirrormanager]::
 Fedora is distributed to millions of systems globally. This would not be
 possible without the donations of time, disk space, and bandwidth by hundreds
@@ -210,6 +216,12 @@ ticketing system and build your community of contributors by allowing them to
 fork your projects and contribute to it via the now-popular pull-request
 mechanism.
 
+PDC https://pdc.fedoraproject.org/[pdc.fp.o]::
+The Product Definition Center is repository and API for storing and querying
+metadata related to packages, product releases, engineering processes and
+artifacts which are required to support automation of release engineering
+workflows.
+
 Release Monitoring https://release-monitoring.org/[release-monitoring.org]::
 Code named https://github.com/fedora-infra/anitya[anitya], this project tracks
 upstream tarball locations and publish notifications to the fedmsg bus when new