defaultBranchName of 'main' for empty repo

fixes atom#2755

Author: wesinator

lib/views/create-dialog.js

@@ -46,7 +46,7 @@ export async function publishRepository(
   if (repository.isEmpty()) {
     wasEmpty = true;
     await repository.init();
-    defaultBranchName = 'master';
+    defaultBranchName = 'main';
   } else {
     wasEmpty = false;
     const branchSet = await repository.getBranches();