Move Piran entry out of us-canada-mex-2024 into a new slovenia-2024 trip.
Rename entry folder to match the post title convention.
Fix us-canada-mex-2024 date_start to 2024-07-21 (first actual US entry).
Applied location_city, location_country, lat, lng, weather_temp_c, weather_desc to all
11 entries (pixelfed-2 through pixelfed-12). Renamed folders from pixelfed-N format to
date-title-slug format. pixelfed-1 (Piran/Slovenia) left untouched.