[Doc]: Added multimaster.sgml

Author: dmpgpro

doc/src/sgml/contrib.sgml

@@ -132,6 +132,7 @@ CREATE EXTENSION <replaceable>module_name</> FROM unpackaged;
  &lo;
  &ltree;
  &mchar;
+ &multimaster;
  &online-analyze;
  &pageinspect;
  &passwordcheck;

doc/src/sgml/filelist.sgml

@@ -138,6 +138,7 @@
 <!ENTITY ltree           SYSTEM "ltree.sgml">
 <!ENTITY mamonsu           SYSTEM "mamonsu.sgml">
 <!ENTITY mchar           SYSTEM "mchar.sgml">
+<!ENTITY multimaster           SYSTEM "multimaster.sgml">
 <!ENTITY oid2name        SYSTEM "oid2name.sgml">
 <!ENTITY online-analyze  SYSTEM "online-analyze.sgml">
 <!ENTITY pageinspect     SYSTEM "pageinspect.sgml">