[Poll Time Widget] Add time widget markdown parser to poll question

The time widget markdown parser is added to poll question header. This
is done giving a `marked` question value to the poll question header and
upon updating the elements using `rendered_markdown`, the `<time>` tags
get updated accordingly. The `poll_widget` test file is modified to
incorporate markdown processing.
Fixes zulip#16821

frontend_tests/node_tests/poll_widget.js

@@ -3,14 +3,26 @@
 const {strict: assert} = require("assert");
 
 const {stub_templates} = require("../zjsunit/handlebars");
-const {zrequire} = require("../zjsunit/namespace");
+const {zrequire, set_global} = require("../zjsunit/namespace");
 const {run_test} = require("../zjsunit/test");
 const $ = require("../zjsunit/zjquery");
 
+const markdown = zrequire("markdown");
+const markdown_config = zrequire("markdown_config");
 const poll_widget = zrequire("poll_widget");
 
 const people = zrequire("people");
 
+zrequire("message_store");
+zrequire("user_groups");
+zrequire("stream_data");
+zrequire("hash_util");
+set_global("page_params", {});
+
+const return_false = () => false;
+const return_true = () => true;
+markdown.initialize([], markdown_config.get_helpers());
+
 run_test("PollData my question", () => {
     const is_my_poll = true;
     const question = "Favorite color?";

static/js/poll_widget.js

@@ -209,10 +209,14 @@ export function activate(opts) {
         const waiting = !is_my_poll && !has_question;
         const author_help = is_my_poll && !has_question;
 
-        const content = elem.find(".poll-widget");
+        const content = elem.find(".poll-question-header");
         elem.find(".poll-question-header").toggle(!input_mode);
-        elem.find(".poll-question-header").append(marked(question));
-        rendered_markdown.update_elements(content);
+        if (/<time:([^>]+)>/.test(question)) {
+            elem.find(".poll-question-header").append(marked(question));
+            rendered_markdown.update_elements(content);
+        } else {
+            elem.find(".poll-question-header").text(question);
+        }
         elem.find(".poll-edit-question").toggle(can_edit);
         update_edit_controls();