Add license-loader

Since xterm and hterm do not have proper comments for their license,
add license-loader to keep their license information in the minimized
bundle file.

js/package-lock.json

@@ -1093,6 +1093,12 @@
         "libapps": {
             "version": "github:yudai/libapps#424e3e95e5346ef0c0c281aaf2ef73463a55b39e"
         },
+        "license-loader": {
+            "version": "0.5.0",
+            "resolved": "https://registry.npmjs.org/license-loader/-/license-loader-0.5.0.tgz",
+            "integrity": "sha512-4p+estbTHilHxOXv/wh8qHndksfINzBT6HGvgIU4sfwWu28kCByHGV57K/HVgSujoFFv2wCITghGbK/qRiRbUQ==",
+            "dev": true
+        },
         "load-json-file": {
             "version": "1.1.0",
             "resolved": "https://registry.npmjs.org/load-json-file/-/load-json-file-1.1.0.tgz",