Update README with usage and publishing instructions

Author: notmandatory

README.md

@@ -1,3 +1,76 @@
 # bdk-swift
 
-A description of this package.
+This project builds a swift package that provides swift language bindings to the [`bdk`] 
+library. The swift language bindings are created by the [`bdk-ffi`] project which is 
+included as a git submodule of this repository. 
+
+## How to Use
+
+To use the swift language bindings provided by the [`bdk-ffi`] project in your xcode iOS 
+or MacOS project add this github repository and select one of the published versions. You 
+may then import the `BitcoinDevKit` library. For example:
+
+```swift
+import BitcoinDevKit
+
+...
+
+let desc = "wpkh([c258d2e4/84h/1h/0h]tpubDDYkZojQFQjht8Tm4jsS3iuEmKjTiEGjG6KnuFNKKJb5A6ZUCUZKdvLdSDWofKi4ToRCwb9poe1XdqfUnP4jaJjCB2Zwv11ZLgSbnZSNecE/0/*)"
+let config = DatabaseConfig.memory(junk: "")
+let wallet = try OfflineWallet.init(descriptor: desc, network: Network.regtest, databaseConfig: config)
+let address = wallet.getNewAddress()
+```
+
+## How to Build and Publish
+
+If you are a maintainer of this project or want to build and publish this project to your 
+own repo use the following steps:
+
+1. Clone this repo and init and update it's [`bdk-ffi`] submodule
+   ```shell
+   git clone https://github.com/bitcoindevkit/bdk-swift
+   git submodule update --init
+   ```
+
+1. Follow the "General" `bdk-ffi` ["Getting Started (Developer)"] instructions.
+
+1. Install the latest version of xcode, download and install the advanced tools.
+
+1. Ensure Swift is installed
+
+1. Install required targets
+   ```shell
+    rustup target add aarch64-apple-ios x86_64-apple-ios
+    ```
+    
+1. Build [`bdk-ffi`] swift bindings and bdkFFI.xcframework.zip
+   ```shell
+   ./build.sh
+   ```
+
+1. Update the `Package.swift` file with the new expected URL for the 
+   `bdkFFI.xcframework.zip` file and new hash as shown at the end of the build.sh script.
+   For example: 
+   ```swift
+           .binaryTarget(
+            name: "bdkFFI",
+            url: "https://github.com/bitcoindevkit/bdk-swift/releases/download/0.1.3/bdkFFI.xcframework.zip",
+            checksum: "c0b1e3ea09376b3f316d7d83575e1cd513fc4ad39ef8cf01120a3a1d7757fb97"),
+   ```
+1. Commit the changed `Package.swift` and tag it with the new version number.
+   ```shell
+   git add Package.swift
+   git commit -m "Bump version to 0.1.3"
+   git tag 0.1.3 -m "Release 0.1.3"
+   git push --tags
+   ```
+
+1. Create a github release for your new tag.
+
+1. Upload the newly created zip to the new github release.
+
+1. Tests the new package in xcode.
+
+[`bdk`]: https://github.com/bitcoindevkit/bdk
+[`bdk-ffi`]: https://github.com/bitcoindevkit/bdk-ffi
+["Getting Started (Developer)"]: https://github.com/bitcoindevkit/bdk-ffi#getting-started-developer