.pullapprove.yml: Add distribution-spec-maintainers

Catching up with [1].

Also mention the new project in GOVERNANCE.md.  I'd still rather drop
the parenthetical entirely and link to a place that listed OCI
Projects, but we don't have a canonical target for that yet
(opencontainers/tob#2) and the current closest instance seems to be
the GitHub section in [2] (which doesn't have the "OCI Project"
words).

[1]: opencontainers/tob#35
[2]: https://www.opencontainers.org/community

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

.pullapprove.yml

@@ -23,6 +23,9 @@ group_defaults:
       - master
 
 groups:
+  distribution-spec:
+    teams:
+      - distribution-spec-maintainers
   image-spec:
     teams:
       - image-spec-maintainers

GOVERNANCE.md

@@ -34,7 +34,7 @@ For projects that are not specifications, a [motion to release](#release-approva
 ## Amendments
 
 The [project governance](#project-governance) rules and procedures MAY be amended or replaced using the procedures themselves.
-The MAINTAINERS of this project governance document is the total set of MAINTAINERS from all Open Containers projects (go-digest, image-spec, image-tools, runC, runtime-spec, runtime-tools, and selinux).
+The MAINTAINERS of this project governance document is the total set of MAINTAINERS from all Open Containers projects (distribution-spec, go-digest, image-spec, image-tools, runC, runtime-spec, runtime-tools, and selinux).
 
 ## Subject templates