Scopes: Spec text for the "scopes" proposal

[szuend]

Preview

Rebased on top of #193 and #194.

This is an early draft of the "scopes" proposal spec text. Sharing it already to get some early feedback and to write it out in the open :)

Done

• Record types for scopes and ranges
• Grammar for scopes and ranges
• Decoding abstract operations/SDOs for scopes and ranges

ToDo

• Add "optionally report an error" handling throughout the decoding where it makes sense.
• Add a section that defines bounds of generated ranges w.r.t. to Ecma262 AST.
• Add normative (or probably informative) section how to correctly utilize the scopes info (similar to Spec: add algorithms for retrieving original & generated positions #195):
  • How to retrieve original function names
  • How to expand stack frames with inlined functions
  • How to condense stack traces with outlined functions