React calendar - Added category component to filter events

[mohammadamer]

#3660
#5175

• New sample
• Bug fix/update
• Related issues: fixes react-calendar -  #3660 react-calendar - why really slow when first opening a page with this webpart on it? #5175

What's in this Pull Request?

This PR contains:
Updates for adding a component for filtering events by category.
Updates to packages.json file because the solution was not building successfully.
Updates to solution package file and README file.

Node Version

Node version used: 12.13.0

Checklist

• My pull request affects only ONE sample.
• My sample builds without any warnings
• I have updated the README.md file's Version history. For new samples, created a new README.md file matching this template
• My README.md has at least one static high-resolution screenshot (i.e. not a GIF) located in the assets folder.
• My README.md contains complete setup instructions, including pre-requisites and permissions required
• My solution includes a .nvmrc file indicating the version of Node.js

React.calendar.-.Categories.filter.mp4

[hugoabernier]

Thank you @mohammadamer for your update! Highly appreciated!.

Thank you for sharing your sample with others - you rock! 👏🥇👩‍💻