Fix go importing

[lollipopman]

This is attempt two, as the first attempt,
bf66a6a, only worked locally when using a go.mod require directive.

When grabbing a module remotely, Go assumes that all dependent code is in the last directory, e.g.

go get github.com/smoeding/tree-sitter-puppet/bindings/go

Grabs everything in /go and below, so compilation fails, since the C code in the parent directory cannot be found.

This problem does not occur in local development however, since the parent directory does exist, which is why adding a require directive masks the problem.

Instead we want to use the go.mod file /tree-sitter-puppet/go.mod and delete tree-sitter-puppet/bindings/go.mod. Then a go get will grab the C code as well.

This is also how other tree-sitter bindings are setup:

https://github.com/tree-sitter-grammars/tree-sitter-yaml

Two other changes are made:

1. Switch the Go tree-sitter bindings from github.com/smacker/go-tree-sitter to github.com/tree-sitter/tree-sitter-puppet, as the latter are unmaintained.
2. Add an indirect dep on github.com/mattn/go-pointer

[smoeding]

I don't use the Go bindings, so I won't be able to help here ;-)