[Feature request] add `resolutions` support

Yarn supports dependencies override with [`resolutions`](https://classic.yarnpkg.com/lang/en/docs/selective-version-resolutions/). In NPM 8.3 there's an equivalent feature [`overrides`](https://docs.npmjs.com/cli/v8/configuring-npm/package-json#overrides).

It would be great if `synp` supported it.

Read Yarn's selective version resolutions documentation and npm's overrides documentation first to compare the requested behaviors. Then locate synp's dependency conversion entry point and existing lockfile handling; done means the converter supports the requested dependency overrides and has coverage for the resulting output.

Written by the indexing model from the issue text.