[New] Adding pre-knowledge about big o notation & translations section

[ranggakd]

I cannot suggest changes to the website so I figured out to:

• [x] add all I discovered on the internet about an introduction into a big o notation to complement the original website.
• [x] add the translations section to create inclusive open-source documentation, so people who speak my language or another language could understand it better there than in the original repo.

Issue related #155