Feature/rb 66 real time chat

[pratibha-growexxer]

• [x] Util for Firebase API (Authentication, Get, Post, Update, Subscription)
• [x] Firebase Middleware for data access
• [x] Util file for Chat Management (Direct Message)
• [x] Realtime update
• [x] Chat window count
• [x] Test cases.
• [x] doc update for feature, packages and how to use the feature.
• [x] Responsive as in mobile app chats comes up on chat list.
• [x] Notification component Dot for new messages
• [x] Skeleton loaders
• [x] Make one chat always visible
• [x] Add search bar in chat list component instead of showing it in whole page. ( https://www.callbell.eu/wp-content/uploads/2019/01/kh0316-facebook-messenger-for-business-link-2-2.png )
• [x] Add avatar in chats. ( https://thispersondoesnotexist.com/ )
• [x] Add online and offline notification ( you are offline. Changes made will not be saved ). ( https://www.npmjs.com/package/react-detect-offline )
• [x] Scrollbars in chat just like youtube
• [x] Mobile view of chats with width 100%
• [x] Searchbar on side ( no chat view just like with chat list )
• [x] Fixed the chat window getting logic
• [x] Last Seen Flag and timestamp of message
• [x] Scroll to bottom
• [x] Group chat support
• [x] Seen flag
• new message dot in notification
• bold the chat list for new unseen message
• add seen flag for current user's message
• update seen flag for messages when clicked from list
• [x] Add Infinite loading in the chats

NOTE: orderBy new message code is commented because currently firebase has issues with indexing

• It is a Optional Feature. It will not be merged in master. So do not delete this PR.

• Feature document updates are done in Feature/readme update #79

[pratibha-growexxer]

[pratibha-growexxer]

@Maulik-growexxer i have attached two sonar screenshots,

1. Passing Gate and Code coverage percentage.
2. Code coverage percentages in components made for real-time-chat

[Maulik-growexxer]

We're not going to merge this, this will be kept as separate feature branch