Document the 2021 edition changes to macros-by-example `pat` metavariables#1135

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mattheww:2022-01_pat_metavariables

Jan 13, 2022

Commits on Jan 9, 2022

Document the 2021 edition changes to macros-by-example `pat` metavariables
mattheww
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Commits on Jan 11, 2022

Clarify that the macro_rules! `pat` behaviour depends on the macro definition's edition
mattheww
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