Mention only the core packages here

[tmigot]

I think we should talk only about the core packages here, and move the extra information to the website. Otherwise, the first contact is too overwhelming.

Instead of focusing on the package, we could focus on the target audience:

• "I want to solve a linear system" -> Go here
• "I want to solve an optimization problem" -> Go here
• "I want to build an optimization method" -> Go here

Originally posted by @abelsiqueira in #1 (comment)

[MaxenceGollier]

@tmigot, i think this issue can be closed now.

[tmigot]

I don't know if it is so clear actually. The idea of this issue was to be very simple for a new user with basic knowledge.

[arnavk23]

@tmigot I really like how it is written on the organization page on github(https://github.com/JuliaSmoothOptimizers), I think we could just use the same and put that also on the website for anyone who contacts the site first to see.