Draft update to the documentation on the topic of tag expressions

[clrudolphi]

🤔 What's changed?

Documentation update to the Scope Bindings page to include information on how to use tag expressions.

⚡️ What's your motivation?

Companion to #911 (Tag Expression support).
This PR should not be merged until 911 is released.

🏷️ What kind of change is this?

• 📖 Documentation (improvements without changing code)

📋 Checklist:

• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "[vNext]" section of the CHANGELOG, linking to this pull request & included my GitHub handle to the release contributors list.

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[gasparnagy]

We can merge this change to #911. Easier to track & review.

[clrudolphi]

Merged into #911