Update peg requirement from 0.7 to 0.8

[dependabot[bot]]

Updates the requirements on peg to permit the latest version.

Release notes

Sourced from peg's releases.

0.8.0

New Features

• #[cache_left_rec] annotation to allow left recursion (#266)
• Return matched token/character from [ ] pattern expression (#234)

Fixes

• Fix Rust grammar for arguments (#261) and type bounds (#279)
• Fix trace feature when using infix!{} (#277)
• Fix #[cache] with grammar lifetime parameters
• Allow clippy::redundant_closure_call lint in generated grammar (#258)

Breaking changes

Most users will not require changes to upgrade from 0.7 to 0.8; these only affect advanced use cases.

• Allow only lifetime, not type, parameters at the grammar level. (type parameters were never properly supported)
• Add 'input lifetime parameter to ParseElem trait so implementations can return tokens by reference. (#268)
• Require Copy on ParseElem::Element to better represent the expectation that they are cheap to copy/move.

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Contributors: @​kevinmehall @​zsol @​neunenak @​fgasperij

Commits

• 40a0049 v0.8.0
• cd3044a Make [] pattern syntax return the matched token/character
• 6838d5d Require ParseElem::Element: Copy
• f09fc34 Add 'input lifetime parameter to ParseElem
• ad7561d Document rule parameters
• 4b7dcaa Expand Rust type and type param grammar
• cdeb247 Test with --trace in GitHub Actions
• 39edc8b Fix #275 change that broke tracing when rule return type is not Copy
• f05f348 Fix trace code in infix!{} for change to mixed_site hygiene
• 73e5579 Merge pull request #275 from neunenak/refactors
• Additional commits viewable in compare view

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