chore: README.md update (#828)

* Revamp README.md.

* Add API reference link.

* Fix typos

* Change order

* Add book emoji

---------

Co-authored-by: Sichan Yoo <[email protected]>

Author: sichanyoo

README.md

@@ -1,24 +1,73 @@
-## Smithy Swift
-
-Smithy code generators for Swift.
-
-**WARNING: All interfaces are subject to change.**
+# <img alt="Smithy" src="https://github.com/smithy-lang/smithy/blob/main/docs/_static/favicon.png?raw=true" width="28"> Smithy Swift
 
 [![License][apache-badge]][apache-url]
 
 [apache-badge]: https://img.shields.io/badge/License-Apache%202.0-blue.svg
 [apache-url]: LICENSE
 
+[Smithy](https://smithy.io/2.0/index.html) code generators for [Swift](https://www.swift.org).
+
+> **⚠️ WARNING**: All interfaces are subject to change.
+
+## Getting Started
+
+- Check out [high-level overview of Smithy](https://smithy.io/2.0/index.html)
+- Try out Smithy by following [the quick start guide](https://smithy.io/2.0/quickstart.html)
+- Apply the Smithy Swift codegen plugin to your Gradle project to generate Swift code
+
+## Feedback
+
+If you'd like to provide feedback, report a bug, request a feature, or would like to bring
+attention to an issue in general, please do so by submitting a GitHub issue to the repo [here](https://github.com/smithy-lang/smithy-swift/issues/new/choose).
+
+This is the preferred mechanism for user feedback as it allows anyone with similar issue or suggestion to engage in conversation as well.
+
+## Contributing
+
+If you are interested in contributing to Smithy Swift, see [CONTRIBUTING](CONTRIBUTING.md) for more information.
+
 ## Development
 
-### Kotlin Modules
+### Module Structure
+
+#### Codegen Modules
 
-* `smithy-swift-codegen` - a module that generates Swift code from Smithy models.
+* `smithy-swift-codegen` - the Kotlin module that generates Swift code from Smithy models.
 
-### Swift Modules
+#### Runtime Modules (under `Sources/`)
 
-* `ClientRuntime` - provides networking, serialization interfaces and implementations using the AWS Swift CRT Bindings for a Swift SDK generated from Smithy Models.
-* `SmithyTestUtil` - provides helper methods for auto-generated Swift unit tests.
+* API modules
+  * `SmithyChecksumsAPI` - protocols & enums for checksum
+  * `SmithyEventStreamsAPI` - protocols & enums for encoding / decoding a single event stream message
+  * `SmithyEventStreamsAuthAPI` - protocols & enums for encoding / decoding event streams and signing event stream messages
+  * `SmithyHTTPAPI` - protocols & enums for HTTP request and response
+  * `SmithyHTTPAuthAPI` - protocols & enums related to signing HTTP requests
+  * `SmithyIdentityAPI` - protocols & enums for identity and identity resolver, which are used to sign requests
+  * `SmithyRetriesAPI` - protocols & enums related to automatic client-side retry behavior
+  * `SmithyWaitersAPI` - protocols & enums related to waiters
+
+
+* Implementation modules
+  * `ClientRuntime` - various runtime functionality used by generated code; contains
+    anything that doesn't squarely fit into other implementation modules below. Has most
+    of the runtime modules as its dependency.
+  * `Smithy` - core functionality used by all clients and other runtime modules, such
+               as custom logger type and generic request and response types
+  * `SmithyChecksums` - implementations for checksum algorithms
+  * `SmithyEventStreams` - implementations for message encoder / decoder and event stream encoder / decoder
+  * `SmithyHTTPAuth` - concrete types related to auth flow
+  * `SmithyHTTPClient` - concrete request type and its builder
+  * `SmithyIdentity` - concrete identity types and identity resolvers for those identity types
+  * `SmithyRetries` -  concrete retry strategy types
+  * `SmithyStreams` - concrete stream types
+  * `SmithyTimestamps` - utility implementations for timestamp shapes in Smithy
+  * `SmithyReadWrite` - generic implementations for runtime serde
+  * `SmithyJSON` - serde implementations specific to JSON
+  * `SmithyXML` - serde implementations specific to XML
+  * `SmithyFormURL` - serde implementations specific to FormURL
+  * `SmithyTestUtil` - helper methods for auto-generated Swift unit tests.
+
+> 📖 For more information on runtime modules, see [the Smithy Runtime Module Documentation in API reference](https://sdk.amazonaws.com/swift/api/awssdkforswift/latest/documentation/awssdkforswift#Smithy-Runtime-Module-Documentation).
 
 ## License
 
@@ -27,4 +76,3 @@ This project is licensed under the Apache-2.0 License.
 ## Security
 
 See [CONTRIBUTING](CONTRIBUTING.md) for more information.
-