DOC: pg_shardman documentation - initial commit

Author: Liudmila Mantrova

doc/src/sgml/contrib.sgml

@@ -145,6 +145,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
  &pgpro-scheduler;
  &pgquerystate;
  &pgrowlocks;
+ &pg-shardman;
  &pgstatstatements;
  &pgstattuple;
  &pgtransfer;

doc/src/sgml/filelist.sgml

@@ -154,6 +154,7 @@
 <!ENTITY pgquerystate    SYSTEM "pgquerystate.sgml">
 <!ENTITY pgrepack        SYSTEM "pgrepack.sgml">
 <!ENTITY pgrowlocks      SYSTEM "pgrowlocks.sgml">
+<!ENTITY pg-shardman     SYSTEM "pg_shardman.sgml">
 <!ENTITY pgstandby       SYSTEM "pgstandby.sgml">
 <!ENTITY pgstatstatements SYSTEM "pgstatstatements.sgml">
 <!ENTITY pgstattuple     SYSTEM "pgstattuple.sgml">