:art: Homepage improvements

[thibmeu]

This issue help users answering the following questions:

• What is the Workbench? What's its aim?
• Who should/can use it?
• Which content is covered?
• How do you contribute content?
• Which companies support it?
• How can I donate to support further development?
• Can I use this as part of my course (University, school, etc.)

What it looks like:

What has been done:

• Partners

  • Logos updated with proper companies
  • Bigger title
  • Shadow on logos

• Feature section

  • Right after the landing screen, features are presented in more detailed for specific set of users: programmers, universities, companies
  • Small picture and text explanation

• Learning

  • Links updated and points to existing content

• Landing screen

  • /start link updated, now points to valid content

• Contribution

  • Contribution via Github or donation