feat(book): Genesis - System Config (#211)

### Description

Adds docs for the `SystemConfig` and structures the book out a bit.

book/src/SUMMARY.md

@@ -1,5 +1,12 @@
 # Summary
 
 - [Introduction](./intro.md)
-- [Glossary](./glossary.md)
+- [Getting Started](./starting/installation.md)
+- [Building](./building/README.md)
+  - [Genesis](./building/genesis/README.md)
+    - [Rollup Config](./building/genesis/rollup-config.md)
+    - [System Config](./building/genesis/system-config.md)
+- [Examples](./examples/README.md)
 - [Contributing](./CONTRIBUTING.md)
+- [Licensing](./LICENSE.md)
+- [Glossary](./glossary.md)

book/src/building/README.md

@@ -0,0 +1,3 @@
+# Building
+
+This section offers in-depth documentation into the various `op-alloy` crates.

book/src/building/genesis/rollup-config.md

@@ -0,0 +1,38 @@
+# Rollup Configs
+
+Rollup configurations are a consensus construct used to configure an Optimism Consensus client.
+When an OP Stack chain is deployed into production or consensus nodes are configured to sync the chain,
+certain consensus parameters can be configured. These parameters are defined in the [OP Stack specs][config].
+
+Consensus parameters are consumed by OP Stack software through the `RollupConfig` type defined in the
+[`op-alloy-genesis`][genesis] crate.
+
+## `RollupConfig` Type
+
+The [`RollupConfig`][rc] type is defined in [`op-alloy-genesis`][genesis].
+
+A predefined rollup config can be loaded from a given L2 chain id using
+the [`rollup_config_from_chain_id`][rcid] method. An example is shown below.
+
+```rust
+use op_alloy_genesis::{OP_MAINNET_CONFIG, rollup_config_from_chain_id};
+
+let op_mainnet_config = rollup_config_from_chain_id(10).expect("infallible");
+assert_eq!(OP_MAINNET_CONFIG, op_mainnet_config);
+```
+
+The `OP_MAINNET_CONFIG` is one of the predefined rollup configs exported by
+the [`op-alloy-genesis`][genesis] crate. Other predefined configs include
+the following.
+
+- `OP_MAINNET_CONFIG`
+- `OP_SEPOLIA_CONFIG`
+- `BASE_MAINNET_CONFIG`
+- `BASE_SEPOLIA_CONFIG`
+
+<!-- Links -->
+
+[rcid]: https://docs.rs/op-alloy-genesis/latest/op_alloy_genesis/rollup/fn.rollup_config_from_chain_id.html
+[rc]: https://docs.rs/op-alloy-genesis/latest/op_alloy_genesis/rollup/struct.RollupConfig.html
+[genesis]: https://crates.io/crates/op-alloy-genesis
+[config]: https://specs.optimism.io/protocol/configurability.html

book/src/building/genesis/system-config.md

@@ -0,0 +1,32 @@
+# System Config
+
+The system configuration is a set of configurable chain parameters
+defined in a contract on L1. These parameters can be changed through
+the system config contract, emitting events that are picked up by
+the [rollup node derivation process][derivation]. To dive deeper
+into the System Config, visit the [OP Stack Specifications][specs].
+
+## `SystemConfig` Type
+
+The [`SystemConfig`][sc] type is defined in [`op-alloy-genesis`][genesis].
+
+Parameters defined in the [`SystemConfig`][sc] are expected to be updated
+through L1 receipts, using the [`update_with_receipts`][update] method.
+
+## Holocene Updates
+
+The [Holocene Hardfork][holocene] introduced an update to the [`SystemConfig`][sc]
+type, adding EIP-1559 parameters to the config.
+
+The [`SystemConfig`][sc] type in [`op-alloy-genesis`][genesis] provides a method
+called [`eip_1559_params`][eip] that returns the EIP-1559 parameters encoded as
+a [`B64`][b64].
+
+[holocene]: https://specs.optimism.io/protocol/holocene/overview.html
+[b64]: https://docs.rs/alloy-primitives/latest/alloy_primitives/aliases/type.B64.html
+[eip]: https://docs.rs/op-alloy-genesis/latest/op_alloy_genesis/system/struct.SystemConfig.html#method.eip_1559_params
+[update]: https://docs.rs/op-alloy-genesis/latest/op_alloy_genesis/system/struct.SystemConfig.html#method.update_with_receipts
+[sc]: https://docs.rs/op-alloy-genesis/latest/op_alloy_genesis/system/struct.SystemConfig.html
+[specs]: https://specs.optimism.io/protocol/system-config.html#system-config
+[derivation]: https://specs.optimism.io/protocol/derivation.html
+[genesis]: https://crates.io/crates/op-alloy-genesis

book/src/examples/README.md

@@ -0,0 +1,5 @@
+# Examples
+
+Examples for working with `op-alloy-*` crates.
+
+TODO: document `op-alloy` crate use and using it with re-exports.

book/src/intro.md

@@ -21,11 +21,11 @@ performance types, traits, and middleware from [alloy][alloy].
 
 To get started with op-alloy, add op-alloy crates as a dependency and take your first steps.
 
-### [Building with op-alloy](./building/rollup-configs.md)
+### [Building with op-alloy](./building/README.md)
 
 A walkthrough of building with op-alloy.
 
-### [Examples](./examples/genesis/loading-a-rollup-config.md)
+### [Examples](./examples/README.md)
 
 This section will give you practical examples of how Alloy can be used in your codebase.