feat: make oembed requests default to json type (#43)

Author: MichaelDeBoey

src/lambda/oembed/oembed.js

@@ -20,7 +20,7 @@ function handler(event, context, callback) {
   const host = getHostname(event, context);
   const params = event.queryStringParameters;
 
-  if (params.format !== 'json') {
+  if (params.format === 'xml') {
     return callback(
       null,
       incorrectParams('unsupported format, only json is supported'),