feat: added markdown editor for editing problems in markdown format (#1805)

src/editors/data/constants/basicProblemTemplates/textInput.js

@@ -0,0 +1,13 @@
+/* eslint-disable */
+const olx =`<problem>
+  <stringresponse type="ci">
+    <additional_answer />
+    <textline size="20"/>
+  </stringresponse>
+</problem>`
+
+const markdown = `= the correct answer
+or= optional acceptable variant of the correct answer
+`
+
+export default { olx, markdown };