fix: peer dependencies doesn't configure correctly

[kamontat]

closes #7203

Summary

If you install decap-cms-app with strict-peer-dependencies enabled. You will get peer dependencies error.

Test plan

Just update dependencies to satisfies peer dependencies

Checklist

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[martinjagodic]

@kamontat this update is not so simple it appears, the builds are failing. Please look into how to best update the dependency. I changed the import, but there are still problems.

[martinjagodic]

I also tried to update unified and other remark dependencies in #7266, but I failed. Jest will not handle them, because they are not common js modules in recent versions.

Let's wait until jest adds support for es6 modules. Until then, I'm closing this PR.