DOCKERFILE_GLOB_PATTERN is too permissive

[freeformz]

We have a dockerfile.go file in at least one repo and it's being detected as belonging to this plugin instead of the Go plugin.

This is likely because the current DOCKERFILE_GLOB_PATTERN is too permissive.

[freeformz]

dockerfile_test.go is also detected as a Dockerfile, instead of a .go file.

[chrisdias]

this is also painful when developing the docker extension :)

[dlech]

@lostintangent, what is the motivation for 950d9f0?

It seems that the standard format is either Dockerfile or *.dockerfile.

I'm going to suggest using only the most common filenames in the extension and users can use the language-specific settings in VSCode if they need to match other files.