Handle "see also" as well as "also see" in index

When cross-referencing, previous work only checked for either
"see" or "also see". This commit adds "see also".

Fixes #1285

CHANGELOG.md

@@ -3,9 +3,9 @@
 
 ## Version 1.6.1
 
-- New 'Add Index Cross-references' feature links "See"/"Also see" references
-  to the relevant location in the index. References that cannot be linked
-  automatically are listed for manual linking
+- New 'Add Index Cross-references' feature links "See"/"Also see"/"See also"
+  references to the relevant location in the index. References that cannot be
+  linked automatically are listed for manual linking
 - Several tools added to support LaTeX/HTML/SVG workflow
 - CP Character Substitutions now include `¬` -> `-`
 - Bad words are loaded when good words file is loaded

src/lib/Guiguts/HTMLConvert.pm

@@ -4248,7 +4248,7 @@ sub indexxref {
     $textwindow->markSet( 'indexendmark', $indexend );    # Since row/col of indexend will change during insertions
     my $indexstart = pop(@ranges);
 
-    my $SEESTR     = '(also )*see';                       # Change this if needed for different languages
+    my $SEESTR     = '(also )?see( also)?';               # Change this if needed for different languages
     my $SEESTRLEN  = length($SEESTR);                     # Approx length just used for advancing search position
     my $seepos     = $indexstart;
     my $seesawnum  = 1;