Add flag to api action to fetch non-JSON data.

If {text:true} or another truthy value is passed as the
`text` option, the api action will use Response.text()
instead of Response.json().

lib/www/client/source/src/store/modules/api/actions.js

@@ -22,7 +22,7 @@ async function api ({state, commit, dispatch}, [resource, init = {}, cb]) {
       await dispatch('setCredentials');
 
       try {
-        return await res.json();
+        return init.text ? (await res.text()) : (await res.json());
       } catch (err) {
         if (err instanceof SyntaxError) {
           if (Number(res.headers.get("Content-Length")) === 0) {