Add 'arm' to list of supported CPU architectures

[samuelmaddock]

Short overview

The Electron project adopted nut.js for use in its tests. Following merging this test, we found it was incompatible with Linux using the arm cpu architecture.

Use case
Although we currently aren't testing the functionality on Linux, being able to install the module on the platform may be helpful in the future.

Detailed description
Linux on ARM may use the process.arch arm rather than arm64. This causes nut.js to report as an incompatible module.

error @nut-tree/nut-js@3.1.2: The CPU architecture "arm" is incompatible with this module.
error Found incompatible module