Document how particles should be represented in SMC

[ciguaran]

Documents how particles should be represented in SMC, providing some examples. Hopefully covers what was answered in this dicussion #464

A few important guidelines and requirements before we can merge your PR:

• [N ] If I add a new sampler, there is an issue discussing it already;
• [Y] We should be able to understand what the PR does from its title only;
• [Y ] There is a high-level description of the changes;
• [Y] There are links to all the relevant issues, discussions and PRs;
• [ Y] The branch is rebased on the latest main commit;
• [Y] Commit messages follow these guidelines;
• [Y] The code respects the current naming conventions;
• [Y] Docstrings follow the numpy style guide
• [Y] pre-commit is installed and configured on your machine, and you ran it before opening the PR;
• [N ] There are tests covering the changes;
• [Y] The doc is up-to-date;
• [ N] If I add a new sampler* I added/updated related examples

Consider opening a Draft PR if your work is still in progress but you would like some feedback from other contributors.

[codecov]

Codecov Report

Merging #582 (fb73280) into main (f5a2a12) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #582   +/-   ##
=======================================
  Coverage   99.14%   99.14%           
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  Files          49       49           
  Lines        2117     2117           
=======================================
  Hits         2099     2099           
  Misses         18       18           

Files	Coverage Δ
blackjax/smc/base.py	100.00% <ø> (ø)