Added docs as asciidoctor with cross platform support. (#5733)

* Added docs as asciidoctor with cross platform support.

* Fixed release script with new doc building mechanism.

doc/api/editbar.adoc

@@ -0,0 +1,30 @@
+== Editbar
+src/static/js/pad_editbar.js
+
+=== isEnabled()
+
+=== disable()
+
+=== toggleDropDown(dropdown)
+Shows the dropdown `div.popup` whose `id` equals `dropdown`.
+
+=== registerCommand(cmd, callback)
+Register a handler for a specific command. Commands are fired if the corresponding button is clicked or the corresponding select is changed.
+
+=== registerAceCommand(cmd, callback)
+Creates an ace callstack and calls the callback with an ace instance (and a toolbar item, if applicable): `callback(cmd, ace, item)`.
+
+Example:
+
+[source, javascript]
+----
+toolbar.registerAceCommand("insertorderedlist", function (cmd, ace) {
+  ace.ace_doInsertOrderedList();
+});
+----
+
+=== registerDropdownCommand(cmd, dropdown)
+Ties a `div.popup` where `id` equals `dropdown` to a `command` fired by clicking a button.
+
+=== triggerCommand(cmd[, item])
+Triggers a command (optionally with some internal representation of the toolbar item that triggered it).