Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.81.1
• OS Version: Windows 10 Pro (19045.2965)

Steps to Reproduce:

1. Try to add a port forward for example to "web_service_1:80" (either via the view or command)
2. The UI gives the error "Forwarded port should be a number or a host:port"

Using dashes would work.

But that would not be so practical.
Especially when working with dev containers, tunneling to other containers mostly happens via their name, which a lot of times includes underscores.