Add grammar docstrings to QASM3 parser #9609

Job	Run time
Format Q# Files	45s
Format	15s
Build and test (windows-latest)	8m 32s
Clippy	42s
Build and test (ubuntu-latest)	6m 9s
Integration tests (windows-latest)	8m 29s
Build and test (macos-14)	7m 52s
Integration tests (ubuntu-latest)	8m 43s
Rust Unit tests (windows-latest)	3m 58s
Check web files	31s
Integration tests (macos-14)	7m 14s
Rust Unit tests (ubuntu-latest)	3m 57s
Rust Unit tests (macos-14)	1s
Status Check	1s
	57m 9s

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