Forc.toml metadata support

docs/book/src/forc/manifest_reference.md

@@ -11,6 +11,7 @@ The `Forc.toml` (the _manifest_ file) is a compulsory file for each package and
     * For the recommended way of selecting an entry point of large libraries please take a look at: [Libraries](./../sway-program-types/libraries.md)
   * `implicit-std` -  Controls whether provided `std` version (with the current `forc` version) will get added as a dependency _implicitly_. _Unless you know what you are doing, leave this as default._
   * `forc-version` - The minimum forc version required for this project to work properly.
+  * `metadata` - Metadata for the project; can be used by tools which would like to store package configuration in `Forc.toml`.
 
 * [`[dependencies]`](#the-dependencies-section) — Defines the dependencies.
 * `[network]` — Defines a network for forc to interact with.
@@ -41,8 +42,64 @@ entry = "main.sw"
 organization = "Fuel_Labs"
 license = "Apache-2.0"
 name = "wallet_contract"
+
+[project.metadata]
+indexing = { namespace = "counter-contract", schema_path = "out/release/counter-contract-abi.json" }
 ```
 
+### Metadata Section in Forc.toml
+
+The `[project.metadata]` section provides a dedicated space for external tools and plugins to store their configuration in `Forc.toml`. The metadata key names are arbitrary and do not need to match the tool's name.
+
+#### Usage
+
+Use any descriptive key name for your metadata table:
+
+```toml
+[project.metadata.any_name_here]
+option1 = "value"
+option2 = "value"
+
+[project.metadata.my_custom_config]
+setting1 = "value"
+setting2 = "value"
+```
+
+Example from an indexing tool:
+
+```toml
+[project.metadata.indexing]
+namespace = "counter-contract"
+schema_path = "out/release/counter-contract-abi.json"
+```
+
+#### Guidelines for Plugin Developers
+
+Best Practices
+
+* Choose clear, descriptive metadata key names
+* Document the exact metadata key name your tool expects
+* Don't require `Forc.toml` if tool can function without it
+* Consider using TOML format for dedicated config files
+
+Implementation Notes
+
+* The metadata section is optional
+* Forc does not parse metadata contents
+* Plugin developers handle their own configuration parsing
+* Choose unique metadata keys to avoid conflicts with other tools
+
+#### Example Use Cases
+
+* Documentation generation settings
+* Formatter configurations
+* Debugger options
+* Wallet integration
+* Contract indexing
+* Testing frameworks
+
+This allows for a streamlined developer experience while maintaining clear separation between core Forc functionality and third-party tools.
+
 ## The `[dependencies]` section
 
 The following fields can be provided with a dependency: