Add dev environment installation instructions for Arch Linux-based systems

[inpv]

Motivation and context

Since Arch Linux-based systems are quite popular, especially in home use and on older hardware, I assume that cvat installation instructions for this type of medium could benefit the community.

How has this been tested?

Tested the installation on a desktop home system (CPU i5 Skylake 6600K, 32 GB RAM, GPU AMD RX 480, pure Arch with XFCE), which is updated daily. The repos enabled are core, extra, community and multilib. AUR is managed by pikaur.
The packages and other related steps required for installation were found by trial and error.

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.

[inpv]

Specified the only supported Python version in the new commit.

[zhiltsov-max]

LGTM, thanks for the contribution!