Tracking Issue for rust-docs improvements

For each of these, we should have a macro stub in place (https://paritytech.github.io/polkadot-sdk/master/frame_support/pallet_macros/index.html), and then put the documentation of the macro in the stub.

All rust-docs should be foundational, use real examples etc.

[ ] call,call_index, compact, weight,
[ ] config, constant, disable_frame_system_supertrait_check, extra_constants, no_default, no_default_bounds
[ ] storage, storage_prefix, storage_version, generate_store, getter, type_value, unbounded, whitelist_storage: https://github.com/paritytech/polkadot-sdk/pull/1714/files
[ ] pallet::pallet, storage_version, without_storage_info
[ ] composite_enum
[ ] genesis_config, build_genesis https://github.com/paritytech/polkadot-sdk/pull/1642/files
[ ] error
[ ] event, generate_deposit
[ ] hooks https://github.com/paritytech/substrate/pull/14578/files
[ ] import_section, pallet_section
[ ] inherent
[ ] origin
[ ] validate_unsigned

[ ] All storage types: https://paritytech.github.io/polkadot-sdk/master/frame_support/storage/types/index.html / https://github.com/paritytech/polkadot-sdk/pull/1714/files
[ ] DispatchResult, DispatchError, DispatchResultWithPostInfo
[ ] trait Hooks https://github.com/paritytech/substrate/pull/14578/files
[ ] trait BuildGenesisConfig
[ ] trait SignedExtension
[ ] trait ValidateUnsigned
[ ] literally everything in frame_system.

Scan a top level runtime, and see which types are often used. Here are some examples, but more can be added. Some groundwork for this is done in https://github.com/paritytech/substrate/pull/14583/files.

The developer-hub will have multiple umbrella crates (see here). These umbrella crates are entry points and contain links to many other crates.

As an example, substrate umbrella crate will link to a bunch of CLI, RPC and consensus related crates.

We expect users to traverse these links and click on them. Therefore these crates should have great documentation.

### Subtasks
- [ ] https://github.com/paritytech/polkadot-sdk-docs/issues/35

paritytech / polkadot-sdk-docs