Add and host a "The Fuel Indexer Book" mdbook

[mitchmindtree]

The indexer is going to become quite the foundational part of the rest of the Fuel ecosystem. Currently, it's a little difficult to approach without having a walk-through from someone who is already familiar.

It would be great to have a book that covers:

• A "Motivations" overview:
  • What goals does fuel-indexer aim to solve.
  • How does it fit into the Fuel ecosystem?
    • What repos/crates does it depend on? (e.g. fuel-vm, fuels, etc)
    • What parts does it enable? (e.g. block explorer? certain forc plugins? other dapps?)
• A "Getting Started" chapter with:
  • System requirements.
  • How to run the fuel-indexer command line tool.
  • How to setup a brand new Rust project that interacts with the fuel-indexer.
• A "Plugins" chapter
  • Purpose of plugins.
  • Why WASM?
  • High-level examples or use-cases for plugins.
  • How to use fuel-indexer with an existing custom plugin in a Rust project.
  • How to write your own plugin with a minimal-as-possible example.

cc @tjsharp1 @SilentCicero @adlerjohn thoughts on this?

If we do want this, we may want to make setting this up a high priority as it will be much easier to make sure new features get documented in the PRs that add them, rather than attempting to document everything retrospectively.

Steps

• [ ] Create a new mdbook project. Look at the Sway repo for an example. Specifically, the docs subdirectory hosts "The Sway Book".
• [ ] Setup automated publishing/hosting. Look at the Sway repo CI for a demonstration on how to automate publishing of the book.
• Write one chapter at a time and solicit feedback under a PR for each. Refer to the Sway book as an example on how to structure different sections. Possibly also The Graph docs might make for an even better example or inspire more ideas.

[adlerjohn]

Looks good, yeah. Whoever works on this if you need help setting up CI feel free to ping me.

[ra0x3]

@mitchmindtree

• I think the "Getting started" is the lowest hanging fruit and good enough to get started/merged
• The "Motivations" and the "Plugins" are important as well.
  • I think I personally have some of those questions (why introduce WASM? Why is it architected the way that it is?) myself - so I think those might take a bit more time
  • So I think these might make good follow ups (unless @tjsharp1 can knock something out relatively quickly for the initial PR, which isn't a super must-have)

[ra0x3]

• Closing, as this was done in https://github.com/FuelLabs/fuel-indexer/pull/24
• If we want to discuss specific sections of the book to add (e.g., Motivations, Plugins mentioned above) we can open new issues for those specific sections