migrate / sync exisiting docs from nuclei-docs

[ehsandeep]

- [x] sync docs from https://github.com/projectdiscovery/nuclei-docs
- [ ] migrate existing language specifics docs + https://github.com/projectdiscovery/nuclei-docs/pull/126
- [ ] configure language selection in docs using [versions](https://mintlify.com/docs/settings/versioning)