Add developer and scm sections.

Sonatype complains if these are missing.

similar-ish changes:
- cl/62226894
- cl/177486560
- jspecify/jspecify@3190434
- jspecify/jspecify@7cce133

I have omitted some values that I'm hoping we don't need (e.g., scm tag, developer timeZone and roles like [we have in Guava](https://github.com/google/guava/blob/0b1c477311b2c7a0a89f5e0ac785084e3ab15d34/pom.xml#L59)). (I am morally opposed in particular to expressing a time zone as an offset of hours from UTC, at least without setting up a reminder to update it for every DST transition :) OK, it looks like [we can actually use a real zone](https://maven.apache.org/pom.html#developers) if we need one.)

PiperOrigin-RevId: 614208351

annotations/pom.xml

@@ -43,6 +43,22 @@
     </license>
   </licenses>
 
+  <scm>
+    <url>http://github.com/google/j2objc</url>
+    <connection>scm:git:git://github.com/google/j2objc.git</connection>
+    <developerConnection>scm:git:ssh://git@github.com/google/j2objc.git</developerConnection>
+  </scm>
+
+  <developers>
+    <developer>
+      <id>tomball</id>
+      <name>Tom Ball</name>
+      <email>tball@google.com</email>
+      <organization>Google</organization>
+      <organizationUrl>https://www.google.com</organizationUrl>
+    </developer>
+  </developers>
+
   <distributionManagement>
     <snapshotRepository>
       <id>sonatype-nexus-snapshots</id>