feat(sds): initial commit for sds demo

[adklempner]

add legend explaining sds concepts
add store queries for missed messages
add history visualization partitioned and ordered by lamport timestamp matchmaking and message sending scenarios
add a theme
better theme
support more than 2 participants

[weboko]

Nice application!

A thing I though of while reviewing:

• can you add to README links to main modules showcasing core SDS logic (e.g waku.svelte.ts, pingpong.svelte.ts etc)

Also, API is easy to follow and I am curious to experiment if it can be simplified even further to something like:

const sds = new SDS(waku, channelId);

sds.send(encoder, { payload });
sds.subscribe(decoder, callback);