Show dummy content to the front page when run with DIFFABLE=1 (#2234)

* Show dummy content to the front page when run with DIFFABLE=1

Author: wilzbach

dlang.org.ddoc

@@ -147,14 +147,14 @@ DDOCKEYVAL2=$(DIVC keyval $1, $(SPANC key key$1, $2:) $(DIVC val val$1, $(TAIL $
 DDSUBLINK=$(LINK2 $(ROOT_DIR)$1.html#$2, $3)
 _=
 
-DBLOG_LATEST_AUTHOR=
-DBLOG_LATEST_DATE=
+DBLOG_LATEST_AUTHOR=A D enthusiast
+DBLOG_LATEST_DATE=December 17, $(YEAR)
 DBLOG_LATEST_LINK=https://dlang.org/blog
-DBLOG_LATEST_TITLE=
-DBLOG_LATEST_AUTHOR2=
-DBLOG_LATEST_DATE2=
+DBLOG_LATEST_TITLE=An article from the DBlog about `DIFFABLE=1`
+DBLOG_LATEST_AUTHOR2=A D-eveloper
+DBLOG_LATEST_DATE2=December 5, $(YEAR)
 DBLOG_LATEST_LINK2=https://dlang.org/blog
-DBLOG_LATEST_TITLE2=
+DBLOG_LATEST_TITLE2=Yet another article that will be replaced with real content
 DMDSRC=$(HTTPS github.com/dlang/dmd/blob/master/src/dmd/$0, $0)
 DOT_PREFIXED=.$1$(DOT_PREFIXED $+)
 DOT_PREFIXED_SKIP=$(DOT_PREFIXED $+)