Add get_latest_version for opengl

[Suraj-Yadav]

If you're updating existing documentation to its latest version, please ensure that you have:

• [x] Ensured the license is up-to-date
• [x] Ensured the icons and the SOURCE file in public/icons/your_scraper_name/ are up-to-date if the documentation has a custom icon
• [x] Ensured self.links contains up-to-date urls if self.links is defined
• [x] Tested the changes locally to ensure:
  • The scraper still works without errors
  • The scraped documentation still looks consistent with the rest of DevDocs
  • The categorization of entries is still good

Also updated base_url's, previous ones didn't exist.