[WIP] Quickstart: DataOwner: Join Network notebook

[ShubhamPalriwala]

Description

Partially closes #6688

• [x] Initialise with basic commands that are already known with 1 liner descriptions
• [x] Command for Logging in into a network with a custom URL
• [x] Functionality Testing
• [ ] Link to previous and next notebook
• [x] Add base64 encoded images
• [x] All UI changes
• [x] Add Title
• [ ] Add Banner Image

Affected Dependencies

None

How has this been tested?

• [x] Thorough Testing
• [ ] Corner cases

Checklist

• [x] I have followed the Contribution Guidelines and Code of Conduct
• [x] I have commented my code following the OpenMined Styleguide
• [x] I have labeled this PR with the relevant Type labels
• [ ] My changes are covered by tests

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[IrinaMBejan]

Great work @ShubhamPalriwala!