Add spectral for OpenAPI (Swagger)

[AMorgaut]

We use spectral to lint our Open API files
It allows us to integrate custom rules like making cache-control HTTP response header mandatory

Information:

• Language: Open API, Async API, JSON Schema
• Linter: Spectral
• URL: https://github.com/stoplightio/spectral

Checklist:

• Only added one linter?
• Is it inside the right language container?
• Is it sorted alphabetically inside the container?
• Does the title follow the template: "Add [LINTER] for [LANGUAGE]."?

[AMorgaut]

Looks like Spectral was already listed in the YAML language section

It works but it means that people only looking at the Open API section won't find spectral but only speccy, while speccy looks to way less advanced and almost abandonned

	specy	spectral
Last commit	5 years ago	2 weeks ago
Last version date	2019-06	2024-04
Contributors	31	92
Used by (repos)	421	2.909
Used by (packages)	21	71
Number of commits	976	2001
Last version	v0.11.0	v6.11.1
Watchers	28	33
Forks	78	233
Stars	823	2.400
License	MIT	Apache 2.0