Omit update check by default

[x29a]

Hey,

what is your opinion on omitting the flutter update check on startup?

Id argue that since the container is disposed after each call, manual upgrading doesnt make any sense and the update check takes quite a while on each run.

This would also contribute towards #5 for faster container startup times.

The appropriate flag is --no-version-check (see here).

After all, the flutter upgrade call works nevertheless if people need it (e.g. for persistent containers).

[matsp]

Sounds like a good idea ☺️

[x29a]

Ill send in the PR soon then, thanks for your feedback!