Add miri to CI

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (5cb5115) 74.93% compared to head (b340f33) 74.73%. Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #75 +/- ## ========================================== - Coverage 74.93% 74.73% -0.21% ========================================== Files 24 24 Lines 3220 3218 -2 ========================================== - Hits 2413 2405 -8 - Misses 807 813 +6 ``` | [Files](https://app.codecov.io/gh/pluots/zspell/pull/75?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pluots) | Coverage Δ | | |---|---|---| | [zspell/src/dict.rs](https://app.codecov.io/gh/pluots/zspell/pull/75?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pluots#diff-enNwZWxsL3NyYy9kaWN0LnJz) | `73.85% <100.00%> (-0.17%)` | :arrow_down: | | [zspell/src/dict/tests.rs](https://app.codecov.io/gh/pluots/zspell/pull/75?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pluots#diff-enNwZWxsL3NyYy9kaWN0L3Rlc3RzLnJz) | `93.47% <ø> (ø)` | | ... and [3 files with indirect coverage changes](https://app.codecov.io/gh/pluots/zspell/pull/75/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=pluots)

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