Firebase extensions do not work with firebase-tools-docker

[fjtheknight]

Hi.
When I run firebase emulator suite using docker, extensions do not work. When I run the emulator suite from cmd, it works.

This is from cmd:

> firebase emulators:start --import=./fb-emulators-import --export-on-exit=./fb-emulators-export

i  emulators: Starting emulators: auth, functions, firestore, hosting, storage, extensions

This is from docker (notice the missing "extensions"):

> firebase emulators:start --import=./fb-emulators-import --export-on-exit=./fb-emulators-export

i  emulators: Starting emulators: auth, functions, firestore, hosting, storage