Package update with lint rules

[pythonhubdev]

• Updated packages to latest version
• Added lint rules
• Updated the example app with latest flutter version

[lig]

Personally, I would like to see those things being a separate PRs.

• Updating dependencies is a routine operation that could be implemented separately.
• Fixing documentation grammar could go in it's own separate PR to prevent it be blocked by less trivial changes.

Also, IMO, linting rules shouldn't change current code style drastically but rather embrace it. I mean, if project mostly uses single quotes that what should we put in as a linting rule.

[pythonhubdev]

Sure will do as required @lig

[vkammerer]

@pythonhubdev I think you split your original PR into too many PRs now: They can't pass the tests individually.
It would be ideal if you only took out the "grammar" fixes in a PR, and left all the rest in a single PR.

So could you open one PR with the contents of #71, #72 and #74 ?

I've checked out your branch https://github.com/pythonhubdev/import_sorter/tree/github_actions and I can see that we'll have to add a few changes to make sure the tests pass and to merge. But I'd rather comment on the PR you'll create than to spread comments across multiple ones

[pythonhubdev]

Sure will do it

[pythonhubdev]

#75 please check this PR