Annotation with brushing tools

[mdacoca]

Motivation and context

Added annotation with brushing tools topic

How has this been tested?

Checklist

• I submit my changes into the develop branch
• I have added a description of my changes into CHANGELOG file
• I have updated the documentation accordingly
• I have added tests to cover my changes
• I have linked related issues (read github docs)
• I have increased versions of npm packages if it is necessary (cvat-canvas,
  cvat-core, cvat-data and cvat-ui)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[bsekachev]

Can you add a couple of lines about using AI tools with "Convert mask to poly" option?
You can use this detector on app.cvat.ai:

Detectors need to be rebuild on this server first. I will look into this.

[zhiltsov-max]

Overall, looks good to me. Probably, 2 more things:

• the imperative speech looks harsh to my taste. From my point, we should describe what the tools to and not what the user must do. It's just my preference, I don't insist.
• Probably, it's better to rename files from brushing to brush after the page text

[nmanovic]

@mdacoca , could you please fix issues from the remark linter?

[nmanovic]

LGTM, we need to find a way to share icons between the UI and documentation. I don't like how we prepare them now.