Added notification message when browser is wrong

[bsekachev]

Motivation and context

Need to notify users if they are using wrong browser (CVAT supports engines Blink and Gecko, not WebKit (like in case of Safary)).

How has this been tested?

Manual testing (Chrome, Firefox, Opera, Yandex)

Checklist

• I submit my changes into the develop branch
• I have added 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.
• I have updated the license header for each file (see an example below)

# Copyright (C) 2020 Intel Corporation
#
# SPDX-License-Identifier: MIT

Resolve #2037

[coveralls]

Pull Request Test Coverage Report for Build 7083

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 69.72%

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Totals
Change from base Build 7079:	0.0%
Covered Lines:	11748
Relevant Lines:	16392

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💛 - Coveralls