Add Postali — free postal codes API (Mexico, Colombia, Spain)

[gomflo]

Adds Postali under Programming Tools, alongside other developer-focused services like jsonstore.io.

Postali is a public REST API for postal codes (códigos postales) covering Mexico, Colombia, and Spain. Truly no-login: no API key, no signup, no monthly request cap.

• Eight endpoints: lookup by code, existence validation, fuzzy search, listings by administrative level, bulk lookups (up to 100 per request)
• HTTPS-only, CORS open (Access-Control-Allow-Origin: *), JSON
• Cacheable lookups (Cache-Control: public, s-maxage=604800) — most traffic served from Cloudflare edge
• Sources: SEPOMEX (MX, ~157k entries), GeoNames (CO ~3.7k, ES ~38k)
• Documentation: https://postali.app/api/docs

Per CONTRIBUTING.md:

• Read intro and confirmed addition is valid
• Description ends with a full-stop
• Added at the bottom of the Programming Tools section
• Spelling and grammar checked