Fix Homebrew install command by removing --no-quarantine flag

[DinanathDash]

This pull request updates the installation instructions in the README.md to clarify how to handle macOS quarantine warnings when installing Stasis via Homebrew.

Improvements to installation instructions:

• Removed the --no-quarantine flag from the Homebrew install command and added guidance for manually removing the quarantine attribute if users encounter a warning.

Closes #13

[DinanathDash]

"Hey! @srimanachanta Just a quick heads-up: I've submitted 6 modular PRs (PRs #17 through #22) to break down a larger set of features and make the review process much easier for you.

Because a few of these PRs touch the same core files (like MenuViewModel.swift and BatteryIndicatorView.swift), merging one might cause merge conflicts in the others. Please review and merge them in whatever order makes the most sense to you!

Once you merge a PR, if GitHub flags any of my remaining open PRs with conflicts, just let me know or leave them be—I will actively monitor the repo and locally rebase my remaining branches against your updated main to resolve the conflicts for you. You won't have to resolve the conflicts yourself!
For the easiest path with the least overlap, my suggested review/merge order is:

1. Fix Homebrew install command by removing --no-quarantine flag #21 (Fix Homebrew install) - Standalone.
2. Add app icons for multiple sizes and update Contents.json #19 (App icons) - Standalone.
3. Refactor time remaining calculation and integrate estimator #18 (Refactor time remaining)
4. Add battery percentage display option in menu bar icon #17 (Battery percentage in menu bar)
5. feat: reflect Low Power Mode in the menu bar battery icon #22 (Low Power Mode icon) - builds slightly on the view from Add battery percentage display option in menu bar icon #17.
6. Add outgoing power visualization to Sankey diagram #20 (Outgoing power Sankey diagram) - heaviest changes.

Thanks for maintaining Stasis! Let me know if you need any adjustments.