chore(linter): add dummy linter entry for Rexx

Add a "none" linter configuration for the Rexx language to provide structure,
while noting that no traditional linter is used and it's primarily for grokkit analyze.

internal/linter/linter.go

@@ -173,7 +173,14 @@ var languages = []Language{
 	{
 		Name:       "Rexx",
 		Extensions: []string{".rx", ".rex", ".rexlib", ".rexx", ".cls"},
-		Linters:    []Linter{}, // No traditional linter; used primarily by `grokkit analyze`
+		Linters: []Linter{
+			{
+				Name:        "none",
+				Command:     "none",
+				Args:        []string{},
+				InstallInfo: "No traditional linter; used primarily by `grokkit analyze`",
+			},
+		},
 	},
 }