reduce code size in index page feature section

[Roger-luo]

I think by sharing some code with "glimpse of bloqade" section, we can reduce the code size in the feature section more, currently, this looks a bit verbose and has no pictures. e.g we don't need to make this part self-contained, but they can be a continuation of the code blocks in "glimpse of bloqade" section.

update: I think also need to be aligned with our readme.