wip(indexeddb): stub _purgeRev method

packages/node_modules/pouchdb-adapter-indexeddb/src/index.js

@@ -150,6 +150,19 @@ function IdbPouch(dbOpts, callback) {
     });
   };
 
+  api._purgeRev = function (docId, rev) {
+    // first, let's remove the document from our docs object store and see what happens to the index
+    return this.remove(docId, rev).then(() => {
+      // then, we inspect the meta object stores
+      // then, we check the auxiliary MR index databases. how do we trigger view rebuilds? do we want actual rebuilds or
+      //   something else?
+      // also of interest could be the native indexeddb find indexes - they shouldn't contain anything since they're
+      //   updated automatically? MR-based find indexes should work as above.
+
+      // also, make sure to remove the entire document if we remove the last leaf that has no branched path?
+    });
+  };
+
   // TODO: this setTimeout seems nasty, if its needed lets
   // figure out / explain why
   setTimeout(function () {