error: cors issue when using post api endpoints

[vince-fugnitto]

Description

When using the post methods (ex: queryUsingPost) there are cors issues regarding the response:

Access to fetch at 'https://open-vsx.org/api/-/query' from origin 'http://localhost:3000' has been blocked by CORS policy:
Response to preflight request doesn't pass access control check: 
No 'Access-Control-Allow-Origin' header is present on the requested resource.
If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

I was able to reproduce the issue both in a Theia-based application and Gitpod directly.

Theia:

Gitpod: