Introduce CI workflow running cargo audit

In order to continuously monitor our dependencies for security
vulnerabilities, we introduce a new CI job that will use `cargo audit`
to check for any known vulnerabilities.

This job is run on a daily schedule. For each new advisory, a new issue
will be created.

Author: tnull

.github/workflows/audit.yml

@@ -0,0 +1,17 @@
+name: Security Audit
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '0 0 * * *'
+
+jobs:
+  audit:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      checks: write
+    steps:
+      - uses: actions/checkout@v3
+      - uses: rustsec/[email protected]
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}

README.md

@@ -4,8 +4,9 @@ Rust-Lightning
 [![Crate](https://img.shields.io/crates/v/lightning.svg?logo=rust)](https://crates.io/crates/lightning)
 [![Documentation](https://img.shields.io/static/v1?logo=read-the-docs&label=docs.rs&message=lightning&color=informational)](https://docs.rs/lightning/)
 [![Safety Dance](https://img.shields.io/badge/unsafe-forbidden-success.svg)](https://github.com/rust-secure-code/safety-dance/)
+[![Security Audit](https://github.com/lightningdevkit/rust-lightning/actions/workflows/audit.yml/badge.svg)](https://github.com/lightningdevkit/rust-lightning/actions/workflows/audit.yml)
 
-[LDK](https://lightningdevkit.org)/`rust-lightning` is a highly performant and flexible 
+[LDK](https://lightningdevkit.org)/`rust-lightning` is a highly performant and flexible
 implementation of the Lightning Network protocol.
 
 The primary crate, `lightning`, is runtime-agnostic. Data persistence, chain interactions,