feat(assets): add animated hero SVG with rm -rf demo

Add hero images for the GitHub README and tinytooltown.com listing:

- hero-animated.svg: CSS keyframe animation with character-by-character
  typing, instant response reveal (error + card), and blinking cursor.
  Pure CSS, GitHub README compatible (10s infinite loop, no JS).
- hero.svg: fully static fallback matching the animated end-state.
- Both show real Format-Suggestion output for 'rm -rf ./build':
  PowerShell error in red, then the PSCommandHelper alias tip card
  with PS equivalent, explanation, note, and example.
- README.md updated to embed the animated hero at the top.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: ericchansen

README.md

@@ -1,3 +1,7 @@
+<p align="center">
+  <img src="assets/hero-animated.svg" alt="PSCommandHelper — type rm -rf ./build, get Remove-Item -Recurse -Force" width="900">
+</p>
+
 # PSCommandHelper
 
 > Learn PowerShell by doing. When you type a bash command that doesn't work in PowerShell, PSCommandHelper suggests the PowerShell equivalent — with an explanation.