Add npmjs badges to the readme

[sequba]

Context

Added 2 badges:

• npm downloads (total)
• npm downloads / month

How has this been tested?

Local markdown preview

Types of changes

• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] New feature or improvement (non-breaking change which adds functionality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Additional language file or change to the existing one (translations)
• [x] Change to the documentation

Related issues:

Fixes #1016

Checklist:

• [x] My code follows the code style of this project.
• [ ] I described the modification in the CHANGELOG.md file.
• [ ] My change requires a change to the documentation.
• [ ] My change requires a migration guide.

[codecov[bot]]

Codecov Report

Merging #1045 (99bc2d9) into develop (6a546f5) will not change coverage. The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #1045   +/-   ##
========================================
  Coverage    95.74%   95.74%           
========================================
  Files          161      161           
  Lines        14085    14085           
  Branches      2974     2974           
========================================
  Hits         13485    13485           
  Misses         584      584           
  Partials        16       16