Guess content type if no header present

Summary:
Changelog: [Network] The network plugin will now detect utf-8 strings if no content header is present

Fixes https://github.com/facebook/flipper/issues/2406

Reviewed By: nikoant

Differential Revision: D29388968

fbshipit-source-id: 7017828a5f3f28dcf220eeda1d30888f1fc5f07a

desktop/flipper-plugin/src/ui/Panel.tsx

@@ -82,8 +82,8 @@ const StyledCollapse = styled(Collapse)({
     background: theme.backgroundWash,
     paddingTop: theme.space.tiny,
     paddingBottom: theme.space.tiny,
-    paddingLeft: 26,
     fontWeight: 'bold',
+    display: 'flex',
     '> .anticon': {
       padding: `5px 0px`,
       left: 8,