add development documentation for tag field implementation

Documentation-develop/HTML.md

@@ -65,3 +65,34 @@ Use with LDAP: `typeAheadLdap`
 
 * Defines the string minlegth, typed by the user, before the first lookup is started. Default is 2.
  
+### data-typeahead-pedantic
+
+* If present, only suggested values are allowed in the input element
+
+
+## Tags Form Element
+ 
+The tags form element depends on Typeahead by default. The following attributes define the tags form element, additional to the attributes for Typeahead (see above).
+
+Mockups can be found in `mockup/typahead.php`
+
+### .data-typeahead-tags
+
+* If present, the field becomes a tag field
+
+### .data-typeahead-tag-delimiters
+
+* List of ascii key codes of the keys which may be pressed to add a new tag when typing.
+
+### .value
+
+* JSON encoded list of key value pairs of existing tags. e.g. 
+  
+  `[{value: "Alaska", key: "AK"}, {value: "Alabama", key: "AL"}]`
+  
+### POST data
+
+* JSON encoded list of key value pairs of the selected tags. e.g.
+
+  `[{value: "Alaska", key: "AK"}, {value: "Alabama", key: "AL"}]`
+