cuepls: support .cue filetype

The initial skeleton of cuepls is based on gopls. Which means that there
is already support for .go, go.mod, and go.work files.

This CL adds support for .cue files alongside the existing file types.

More vestiges of Go (gopls) code will be removed in later CLs.

For #142

Signed-off-by: Paul Jolly <paul@myitcv.io>
Change-Id: Ia5028fbf7e27b3d48c9865ec803e3f73f0278f34

internal/golangorgx/gopls/cache/snapshot.go

@@ -323,6 +323,8 @@ func fileKind(fh file.Handle) file.Kind {
 		return file.Sum
 	case ".work":
 		return file.Work
+	case ".cue":
+		return file.CUE
 	}
 	return file.UnknownKind
 }

internal/golangorgx/gopls/file/kind.go

@@ -24,6 +24,8 @@ const (
 	Tmpl
 	// Work is a go.work file.
 	Work
+	// CUE is a CUE source file
+	CUE
 )
 
 func (k Kind) String() string {
@@ -38,6 +40,8 @@ func (k Kind) String() string {
 		return "tmpl"
 	case Work:
 		return "go.work"
+	case CUE:
+		return "cue"
 	default:
 		return fmt.Sprintf("internal error: unknown file kind %d", k)
 	}
@@ -58,6 +62,8 @@ func KindForLang(langID string) Kind {
 		return Tmpl
 	case "go.work":
 		return Work
+	case "cue":
+		return CUE
 	default:
 		return UnknownKind
 	}