Mac OS Setup Instructions

[s2t2]

Adds instructions for setting up the repository on Mac OS.

Details:

• Uses homebrew to install system libraries on Mac, and Anaconda to manage the virtual environment.

• Pins specific versions of system library dependencies (protoc version 3.21.12 and ffmpeg version 7.1.1), to prevent differences between setups. Also pins poetry package to version 3.1.2.

• Updates the "Makefile" to use poetry-based commands instead of virtualenv-specific commands that won't work if a Mac user is using Anaconda instead.

• Splits the setup instructions into three separate system-specific documents (Mac vs Linux vs Docker).

• Updates the GitHub Actions workflow file to run tests against Mac OS as well.

• Fixes a test that was passing on Linux and newer versions of Mac (ARM64), but failing on intel-based Macs (x86_64) due to slight differences in floating point math.

• We are noticing an issue when trying to use the dm-reverb package on Mac. We attempted to overcome the issue by conditionally installing dm-reverb-macos on Mac, however that doesn't work either. We are deciding to move forward with merging this Mac OS setup, despite the dm-reverb issues, because it only affects a small part of the codebase (the RL replay buffers). We are adding a note to the Mac OS setup instructions about this, and creating a separate issue to follow up with fixing the dm-reverb installation on Mac. Fix installation of dm-reverb on Mac #102

[s2t2]

Looks like we are running into issues with trying to usedm-reverb on Mac OS.

google-deepmind/reverb#11

google-deepmind/reverb#128

[s2t2]

We are deciding to move forward with merging this Mac OS setup, despite the dm-reverb issues, which only affect a small part of the codebase (the RL replay buffers). We will add a note to the Mac OS setup instructions, and create a separate issue to follow up with fixing the dm-reverb installation on Mac.