Update release version to v0.1.2.b.1 and enhance macOS support in terminal.py and install.sh

- Updated the release version in index.html and version.txt to v0.1.2.b.1.
- Added macOS detection and installation instructions for Python 3 in install.sh.
- Refactored terminal.py to include first-class support for macOS, updating distribution prompts and compatibility checks.
- Improved user experience by integrating Homebrew installation prompts for Python 3 on macOS.

index.html

@@ -46,7 +46,7 @@
     <div class="hero__metrics">
       <div class="metric">
         <p class="metric__label">Current release</p>
-        <p class="metric__value">v0.1.2.b</p>
+        <p class="metric__value">v0.1.2.b.1</p>
       </div>
       <div class="metric">
         <p class="metric__label">Supported families</p>