Shot hash should include base template and CSS too

[Simon Willison]

Screenshots currently won't be regenerated if I change the base template or modify the CSS:

til/generate_screenshots.py

Lines 35 to 38 in c3d1cc4

 # The shot_hash incorporates a hash of all of row.html 
 row_html_hash = hashlib.md5( 
     (root / "templates" / "row.html").read_text().encode("utf-8") 
 ).hexdigest()