Remove `packageManager` property from the template's `package.json` if it differs from the selected package manager.

[beeman]

The task that installs the dependencies should remove the packageManager from package.json if it exists and it's not the same as the selected package manager. If the script decides to remove it, it should print a message to the console to warn about potential incompatibilities.

This prevents issues like #100 and will make the tool compatible with more templates as currently, package managers like yarn and pnpm will error if they find this property and are incompatible with it.

[Afoxcute]

is this still available for contribution? @beeman