Add basic deny.toml file (#58)

### Checklist

* [x] I have read the [Contributor Guide](../../CONTRIBUTING.md)
* [x] I have read and agree to the [Code of
Conduct](../../CODE_OF_CONDUCT.md)
* [x] I have added a description of my changes and why I'd like them
included in the section below

### Description of Changes

Adds a basic cargo-deny configuration as well as a CI step to run it on
every run.

.github/workflows/rust-ci.yml

@@ -25,6 +25,7 @@ jobs:
         run: |
           rustup component add clippy
           cargo clippy --all-targets --all-features -- -D warnings
+      - uses: EmbarkStudios/cargo-deny-action@v1
 
   cargo-hack:
     runs-on: ubuntu-latest

deny.toml

@@ -0,0 +1,32 @@
+[advisories]
+vulnerability = "allow"
+unmaintained = "allow"
+
+[bans]
+multiple-versions = "deny"
+deny = [
+]
+
+skip = [
+]
+
+[sources]
+unknown-registry = "deny"
+unknown-git = "allow"
+allow-registry = [
+    "https://github.com/rust-lang/crates.io-index",
+]
+
+[licenses]
+unlicensed = "deny"
+allow-osi-fsf-free = "neither"
+# We want really high confidence when inferring licenses from text
+confidence-threshold = 0.92
+copyleft = "deny"
+allow = [
+    "Apache-2.0",
+    "MIT",
+    "Unicode-DFS-2016",
+]
+exceptions = [
+]