Added missing license

Author: taras

stream-helpers/deno.json

@@ -5,6 +5,7 @@
     "effection": "jsr:@effection/effection@^3",
     "immutable": "npm:immutable@^5"
   },
+  "license": "MIT",
   "exports": {
     ".": "./mod.ts",
     "./test-helpers": "./test-helpers.ts"