Add openSUSE instructions and refactor README

[fentras]

This pull request closes #2711 and also refactors the README file according to these changes:

• Fixed uneven spacing and indentation
• Updated hyphens to em dashes where applicable
• Capitalized titles
• Removed https:// from link titles
• Updated the headers structure and table of contents
• Updated Install Instructions to include a no-installation method

[nesbox]

Hi, we need make command or cmake --build . --parallel

[fentras]

Hi, we need make command or cmake --build . --parallel

Yeah, I removed make -j4 since the command was already in the Install Instructions section but I didn't notice the Arch section missing another cmake command. Will fix that right now.

[nesbox]

Thank you