improve chain README; add coverage badges to repo README

Author: kyle-johnson

.changeset/small-parrots-vanish.md

@@ -0,0 +1,5 @@
+---
+"abortcontroller-chain": patch
+---
+
+Explain _why_ chaining is useful.

README.md

@@ -1,13 +1,19 @@
-[AbortControllers](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) and [AbortSignals](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) are awesome, but they are extremely simple building blocks.
+# AbortController Utilities
+[![GitHub Workflow Status](https://img.shields.io/github/workflow/status/kyle-johnson/abortcontroller-utils/CI)](https://github.com/kyle-johnson/abortcontroller-utils/actions)
 
-These utilities bring a few more _bulding blocks_ to make use of AbortController/AbortSignal a bit more concise for common use cases.
+[AbortControllers](https://developer.mozilla.org/en-US/docs/Web/API/AbortController) and [AbortSignals](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) are awesome, but they are very simple building blocks.
+
+These utilities bring a few more bulding blocks to make common use cases easy, such as [creating a deadline](./packages/deadline) or [chaining multiple signals into one controller](./packages/chain).
 
 ## [`abortcontroller-chain`](./packages/chain)
 [![npm](https://img.shields.io/npm/v/abortcontroller-chain)](https://www.npmjs.com/package/abortcontroller-chain)
+[![Codecov](https://img.shields.io/codecov/c/github/kyle-johnson/abortcontroller-utils?flag=chain&label=coverage)](https://app.codecov.io/gh/kyle-johnson/abortcontroller-utils/)
 
 Contect an AbortController to one or more AbortSignals.
 
 ## [`abortcontroller-deadline`](./packages/deadline)
 [![npm](https://img.shields.io/npm/v/abortcontroller-deadline)](https://www.npmjs.com/package/abortcontroller-deadline)
+[![Codecov](https://img.shields.io/codecov/c/github/kyle-johnson/abortcontroller-utils?flag=deadline&label=coverage)](https://app.codecov.io/gh/kyle-johnson/abortcontroller-utils/)
+
 
 Easily create an AbortController which aborts after a specified amount of time (a _deadline_).

packages/chain/README.md

@@ -5,7 +5,7 @@
 [![license](https://img.shields.io/npm/l/abortcontroller-chain)](https://github.com/kyle-johnson/abortcontroller-utils/blob/main/packages/chain/LICENSE)
 [![Codecov](https://img.shields.io/codecov/c/github/kyle-johnson/abortcontroller-utils?flag=chain&label=coverage)](https://app.codecov.io/gh/kyle-johnson/abortcontroller-utils/)
 
-Chain multiple signals into one controller: if any of the signals aborts, the controller will be aborted.
+Chain multiple signals into one controller: if any of the signals aborts, the controller will be aborted. This is particularly useful since most APIs only accept a _single_ AbortSignal input ([`fetch()`](https://developer.mozilla.org/en-US/docs/Web/API/fetch), [axios](https://github.com/axios/axios#cancellation), the [AWS SDK](https://aws.amazon.com/blogs/developer/abortcontroller-in-modular-aws-sdk-for-javascript/), etc).
 
 Works with browsers, NodeJS (16+), and spec-compliant polyfills.