Move `mocha` into `peerDependendencies` and add `v10`

[kraenhansen]

In its current form, this package adds it's own dependency on a pinned version of mocha which isn't necessary as it'll always be installed into a project that already has mocha installed.

https://github.com/daniellockyer/mocha-github-actions-reporter/blob/5870622e543d6067d460f1065c19164a1ddc5e88/package.json#L18

Instead, I suggest moving this into peerDependencies and add ^10 if none of the breaking changes affect this package.