render Markdown and support link navigation in KDoc comments

idea/testData/editor/quickDoc/OnMethodUsageWithMarkdown.kt

@@ -0,0 +1,26 @@
+/**
+ * Some documentation. **Bold** *underline* `code` foo: bar (baz) [quux] <xyzzy>
+ *
+ * [Kotlin](http://www.kotlinlang.org)
+ *
+ * [C]
+ *
+ * [See this class][C]
+ */
+fun testMethod() {
+
+}
+
+class C {
+}
+
+fun test() {
+    <caret>testMethod(1, "value")
+}
+
+//INFO: <b>internal</b> <b>fun</b> testMethod(): Unit<br/><p><p>Some documentation. <strong>Bold</strong> <em>underline</em> <code>code</code> foo: bar (baz) <a href="psi_element://quux">quux</a> </p>
+//INFO: <p>a href="http://www.kotlinlang.org">Kotlin</a></p>
+//INFO: <p><a href="psi_element://C">C</a></p>
+//INFO: <p><a href="psi_element://C">See this class</a></p>
+//INFO:
+//INFO: </p>