document JAVASCRIPTKIT_WITHOUT_BIGINTS flag

Author: j-f1

README.md

@@ -71,15 +71,15 @@ a few additional steps though (you can skip these steps if your app depends on
 )
 ```
 
-2. Add an explicit import in the code that executes **before* you start using `await` and/or `Task`
-APIs (most likely in `main.swift`):
+1. Add an explicit import in the code that executes **before** you start using `await` and/or `Task`
+   APIs (most likely in `main.swift`):
 
 ```swift
 import JavaScriptEventLoop
 ```
 
-3. Run this function **before* you start using `await` and/or `Task` APIs (again, most likely in
-`main.swift`):
+3. Run this function **before** you start using `await` and/or `Task` APIs (again, most likely in
+   `main.swift`):
 
 ```swift
 JavaScriptEventLoop.installGlobalExecutor()
@@ -125,21 +125,21 @@ asyncButtonElement.onclick = .object(JSClosure { _ in
 _ = document.body.appendChild(asyncButtonElement)
 ```
 
-## Requirements 
+## Requirements
 
 ### For developers
 
-- macOS 11 and Xcode 13.2 or later versions, which support Swift Concurrency back-deployment. 
-To use earlier versions of Xcode on macOS 11 you'll have to 
-add `.unsafeFlags(["-Xfrontend", "-disable-availability-checking"])` in `Package.swift` manifest of
-your package that depends on JavaScriptKit. You can also use Xcode 13.0 and 13.1 on macOS Monterey,
-since this OS does not need back-deployment.
+- macOS 11 and Xcode 13.2 or later versions, which support Swift Concurrency back-deployment.
+  To use earlier versions of Xcode on macOS 11 you'll have to
+  add `.unsafeFlags(["-Xfrontend", "-disable-availability-checking"])` in `Package.swift` manifest of
+  your package that depends on JavaScriptKit. You can also use Xcode 13.0 and 13.1 on macOS Monterey,
+  since this OS does not need back-deployment.
 - [Swift 5.5 or later](https://swift.org/download/) and Ubuntu 18.04 if you'd like to use Linux.
   Other Linux distributions are currently not supported.
 
 ### For users of apps depending on JavaScriptKit
 
-Any recent browser that [supports WebAssembly](https://caniuse.com/#feat=wasm) and required 
+Any recent browser that [supports WebAssembly](https://caniuse.com/#feat=wasm) and required
 JavaScript features should work, which currently includes:
 
 - Edge 84+
@@ -149,7 +149,7 @@ JavaScript features should work, which currently includes:
 - Mobile Safari 14.8+
 
 If you need to support older browser versions, you'll have to build with
-`JAVASCRIPTKIT_WITHOUT_WEAKREFS` flag, passing `-Xswiftc -DJAVASCRIPTKIT_WITHOUT_WEAKREFS` flags
+`JAVASCRIPTKIT_WITHOUT_WEAKREFS` and `JAVASCRIPTKIT_WITHOUT_BIGINTS` flags, passing `-Xswiftc -DJAVASCRIPTKIT_WITHOUT_WEAKREFS -Xswiftc -DJAVASCRIPTKIT_WITHOUT_BIGINTS` flags
 when compiling. This should lower browser requirements to these versions:
 
 - Edge 16+