feat(vscode): add file icons for terragrunt HCL files (#127)

* feat(vscode): add file icons for terragrunt HCL files

Register light/dark SVG icons for terragrunt.hcl, terragrunt.stack.hcl,
and terragrunt.values.hcl via the language contribution's icon field.

* chore(vscode): update terragrunt file icon artwork

* fix: light and dark icons

Signed-off-by: Diogenes Fernandes <diofeher@gmail.com>

---------

Signed-off-by: Diogenes Fernandes <diofeher@gmail.com>

Author: diofeher

vscode-extension/images/icon-dark.svg

@@ -34,7 +34,11 @@
 					"terragrunt.stack.hcl",
 					"terragrunt.values.hcl"
 				],
-				"configuration": "./language-configuration.json"
+				"configuration": "./language-configuration.json",
+				"icon": {
+					"light": "./images/icon-dark.svg",
+					"dark": "./images/icon-light.svg"
+				}
 			}
 		],
 		"grammars": [