Add JSON-RPC fallback and MEV blocking tutorial

[miohtama]

What was wrong?

Flaky JSON-RPC and frontrunning are harming the users of Web3.py library.

How was it fixed?

Adding a tutorial on advanced MEV protection and JSON-RPC fallback configuration for Web3.
This tutorial uses a special MultiProviderWeb3 class from web3-ethereum-defi package which allows complex JSON-RPC configurations.

The tutorial is linked in the external resources documentation section.

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Art by Joan Stark

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[wolovim]

sorry @miohtama, this just fell off my radar. thanks for the link! your other recent swap example(s) come to mind as good potential additions here too.