Documentation #42

Started working on the documentation website.
There are 14 pages:

• Home
• Installation and Testing
• Quick Start
• Prerequisites
• Sparse Matrix class
• Mass Matrix class
• Vector Function class
• Jacobian Matrix class
• Solution Manager class
• Solver Options class
• Solving DAE system
• Utilities
• Examples
• CHANGELOG

This documentation could be better. Something can still be not clear or awkwardly worded.
Please feel free to contribute/fix typos and errors or even rewrite whole bits of the documentation!

Link to the repo:
https://github.com/dae-cpp/dae-cpp.github.io/tree/main/docs