Adding the ability to use invisible edges

[knsv]

📑 Summary

Re-introducing the feature of invisible lines into mermaid.

Resolves #2805, #3192

📏 Design Decisions

Describe the way your implementation works or what design decisions you made if applicable.

📋 Tasks

Make sure you

• 📖 have read the contribution guidelines
• 💻 have added unit/e2e tests (if appropriate)
• 📓 have added documentation (if appropriate)
• 🔖 targeted develop branch

[pbrolin47]

OK to merge