Build(deps-dev): bump typescript from 3.8.3 to 3.9.6

Bumps [typescript](https://github.com/Microsoft/TypeScript) from 3.8.3 to 3.9.6.
- [Release notes](https://github.com/Microsoft/TypeScript/releases)
- [Commits](https://github.com/Microsoft/TypeScript/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -247,7 +247,7 @@
     "tmp": "0.2.1",
     "tsd": "^0.11.0",
     "ts-mocha": "^7.0.0",
-    "typescript": "^3.8.3"
+    "typescript": "^3.9.6"
   },
   "engines": {
     "node": "^10.16.3",