Add support for Apple Silicon

[odow]

This PR adds support for apple silicon. I've tested that it works locally.

Closes #61

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (87f8884) 93.66% compared to head (a85d6dd) 93.66%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #88 +/- ## ======================================= Coverage 93.66% 93.66% ======================================= Files 3 3 Lines 379 379 ======================================= Hits 355 355 Misses 24 24 ``` | [Files Changed](https://app.codecov.io/gh/chkwon/PATHSolver.jl/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Changhyun+Kwon) | Coverage Δ | | |---|---|---| | [src/PATHSolver.jl](https://app.codecov.io/gh/chkwon/PATHSolver.jl/pull/88?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Changhyun+Kwon#diff-c3JjL1BBVEhTb2x2ZXIuamw=) | `83.33% <0.00%> (ø)` | |

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[odow]

Oh, I don't have permission to install https://github.com/marketplace/cirrus-ci here.

@chkwon if you have time, can you go to https://github.com/marketplace/cirrus-ci, scroll to the bottom, and follow the prompts to install a public plan?

[odow]

merging because I've tested this locally. We can add CI later

[odow]

actually I'll delete the Cirrus file until needed