Include [YYYY]? to uncertain original-date (#4269)

Discussed in #4262

Author: Joseph Reagle

chicago-fullnote-bibliography.csl

@@ -714,7 +714,14 @@
         <text variable="original-publisher-place"/>
         <text variable="original-publisher"/>
       </group>
-      <date variable="original-date" form="text" date-parts="year"/>
+      <choose>
+        <if is-uncertain-date="original-date">
+          <date variable="original-date" form="numeric" date-parts="year" prefix="[" suffix="?]"/>
+        </if>
+        <else>
+          <date variable="original-date" form="numeric" date-parts="year"/>
+        </else>
+      </choose>
     </group>
   </macro>
   <macro name="reprint-note">