tools/license.sh: add CC-BY-4.0 license

@vscode/codicons is under CC-BY-4.0

Change-Id: I6117a4fb681c59b202d9377269ae471b187b6275
Reviewed-on: https://go-review.googlesource.com/c/vscode-go/+/447261
Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Robert Findley <rfindley@google.com>
TryBot-Result: kokoro <noreply+kokoro@google.com>

Author: hyangah

tools/license.sh

@@ -38,6 +38,7 @@ NG=$(echo "${ALL_LICENSES}" | jq '
   "Apache-2.0": 1,
   "BSD-2-Clause": 1,
   "BSD-3-Clause": 1,
+  "CC-BY-4.0": 1,
   "ISC": 1,
   "MIT": 1,
   "Unlicense": 1,