KCD: Add slides Building Internal Platforms with Crossplane

[clementblaise]

Before submitting a pull request, please make sure the following is done:

Checklist

• Fork the repository and create your new branch from master.
• Please mention the name of community in Pull Request title.
• Git Commit Messages
  • Use the present tense (Also in Pull Request title): "Add feature" not "Added feature"
  • Use the imperative mood (Also in Pull Request title): "Move cursor to..." not "Moves cursor to..."
  • Use rebase to squash/fixup dummy/unnecessary commits into only one commit.

[ydFu]

@clementblaise thanks !