WIP: Add slate editor with read only support

[RajendrasinhParmar]

Description of what you did:

Implemented a Text Editor using the slate library so that users can create posts in basic rich text format.

Library used: slate framework

This PR is currently a work in progress.

My PR is a:

• [ ] 🐛 Bug fix closes #number
• [ ] 💅 Enhancement closes #number
• [x] 🚀 New feature closes #183

Main update on the:

• [x] orca-api
• [x] orca-frontend
• [ ] create-orca-app
• [ ] other

[RajendrasinhParmar]

@DimiMikadze Can you have a very quick look into the way I've implemented the TextEditor component?

[DimiMikadze]

@RajendrasinhParmar thank you very much for working on this issue. The code looks great!

Unfortunately, I don't have time anymore to contribute to this project due to work, and I've decided to close the ElevenSymbols project and move this repository to my personal Github account.

I'll add you as a core contributor for this project in the readme.md file.

Once again, thanks for all the great work!