Add examples of using PGML tags to the PGML lab problem.

The examples are in the "Substitutions" drop down menu of "Examples".
In particular there is an exmaple demonstrating how to use PGML tags for
placement of the feedback button with MultiAnswer problems that use
`singleResult => 1`.

assets/pg/PGMLLab/PGML-lab.pg

@@ -461,6 +461,64 @@ TEXT(tag(
 								ENDPGML
 						]
 					],
+					[
+						'Tags' => [
+							<<~ 'END_PG',
+							loadMacros('parserMultiAnswer.pl', 'parserPopUp.pl');
+							$ma = MultiAnswer(DropDown([ [ 'minimum', 'maximum' ] ], 1), 4)->with(
+								singleResult => 1,
+								checker      => sub {
+									my ($cor, $stu) = @_;
+									return $cor->[0] == $stu->[0] && $cor->[1] == $stu->[1]
+										? 1
+										: 0;
+								}
+							);
+							END_PG
+							<<~'ENDPGML'
+								A tag is a "div" by default. HTML attributes can be set via an array in the
+								first option.  The only other allowed tag type is a span. To switch to a
+								span add 'span' to the beginning of the attribute array.  The second tex
+								option and the third ptx option are used to set the output for the TeX and
+								PTX display modes. The format of the tex option is an array containing two
+								strings.  The first string is the TeX code to insert before the content,
+								and the second the TeX code to insert after the content.  The format of the
+								ptx option is similar to the format for the first html. It is an array with
+								the tag name (required), optionally followed by an array of attributes, and
+								optionally a separator.
+
+								[<Dangerous content.>]{
+									[ 'span', class => 'p-1 alert alert-danger', role => 'alert' ]
+								}{
+									[ '{\color{red}', '}' ]
+								}{
+									['alert']
+								}
+
+								Tags may contain other PGML content and answers. Note that a span tag may
+								not contain new lines, tables, or anything else that would be invalid in a
+								span.  Basically only text elements are valid. However, div tags may
+								contain pretty much anything.
+
+								[<
+								    This is an equation [`x + 3 = 5`].
+
+									The solution to the above equation is [_]{2}.
+								>]{ [ style => 'border: 1px solid black; padding: 1rem;' ] }
+
+								One useful application is when using the parserMultiAnswer.pl macro with
+								singleResult answers. Wrap the answers in in a div tag with the
+								"ww-feedback-container" class to tell PG where to place the feedback
+								button. The feedback button will be placed at the end of the containing div
+								tag.
+
+								[<
+									The [_]{$ma} value of [`f(x)`] is [_]{$ma} for the function
+									[`f(x) = 4 - x^2`].
+								>]{ [ class => 'ww-feedback-container' ] }
+								ENDPGML
+						]
+					],
 				),
 				Examples(
 					'Inline formatting',
@@ -975,7 +1033,8 @@ TEXT(tag(
 						'[@ perl-command @]* (no escaping)',
 						'[@ perl-command @]** (parse results)',
 						'[% comment %]',
-						'[&lt;url&gt;] (not implemented)',
+						'[&lt;tag&gt;]{html}{tex}{ptx}',
+						'[[url]] (not implemented)',
 						'[!image!]{source}{width}{height}',
 					),
 					Menu(