That was pulled out to gpuweb#1586

That was pulled out to gpuweb#1586

* WGSL: describe ref ptr

- Add "memory view types" section
  - Defines reference type and pointer type
  - gives use cases and examples
  - Compares to other lanaguages
- Adds:
  - composite reference sub-expressions
  - address-of expression (unary &)
  - indirection expression (unary *)
  - variable identifier expression
  - const identifier expression
  - formal parmaeter identifier expression

TODO: grammar update for unary * and unary &

Alternate to #1368
Fixes: #1456

* Remove -> void from the newer examples

* Apply review feedback

Addressed feedback from @alan-baker and @ben-clayton

Fixed typos, examples, links, and added an example showing
what happens when the expression in a return statement is a reference.

* Fix word

* Fix types in comments in examples

* Add grammar rule for unary &, unary *; address feedback

- Added the grammar rule for address-of and indirection
- Fixed algorithm name text (was copypasta)
- Fixed example in the assignment-statement section.

* Fix typo in the add_one example

* Make address-of, indirection defined terms

Improve cross-linking.

* Add missing access qualifier in example

* One more rename of "composite reference component expression"

* Fix caption on structure-member reference expression

* Convert ptr syntax examples to use a function declaration

Applies feedback from @kvark review.
Using a complete and valid function definition allows the example
to be valid WGSL.

- changed the pointer-to-uniform example to pointer-to-function,
  because pointer-to-uniform arguments won't be valid. (Sorry, that's a
  restriction from baseline SPIR-V in Vulkan restriction.)

* Remove "Const identifier expression"

That was pulled out to #1586

* For assignment statement, spell out memory *locations*

* Add cross-reference to function-param expression

Issue gpuweb#792