feat: improvements on nitro landing page

[tikikun]

Nitro vs OpenAI

• Wrong api endpoint @urmauur
  

Remove Speed section

• Please remove the speed section since we will not do speed comparison

Hero CTAs

• "Github" Button -> lead to the release page of nitro at https://github.com/janhq/nitro/releases
• Try to have a Github logo on the Github button (see SuperAGI's below)

Engine Logos

• Please add logo to the engine

[dan-menlo]

@tikikun @urmauur I have edited the Task Description to be more specific