adopt SSWG security guidelines (#209)

* add SECURITY.md detailing the security process
* Update readme.md

SECURITY.md

@@ -0,0 +1,43 @@
+# Security
+
+This document specifies the security process for the Swift AWS Lambda Runtime project.
+
+## Disclosures
+
+### Private Disclosure Process
+
+The Swift AWS Lambda Runtime maintainers ask that known and suspected vulnerabilities be
+privately and responsibly disclosed by emailing
+[sswg-security-reports@forums.swift.org](mailto:sswg-security-reports@forums.swift.org)
+with the all the required detail.
+**Do not file a public issue.**
+
+#### When to report a vulnerability
+
+* You think you have discovered a potential security vulnerability in Swift AWS Lambda Runtime.
+* You are unsure how a vulnerability affects Swift AWS Lambda Runtime.
+
+#### What happens next?
+
+* A member of the team will acknowledge receipt of the report within 3
+  working days (United States). This may include a request for additional
+  information about reproducing the vulnerability.
+* We will privately inform the Swift Server Work Group ([SSWG][sswg]) of the
+  vulnerability within 10 days of the report as per their [security
+  guidelines][sswg-security].
+* Once we have identified a fix we may ask you to validate it. We aim to do this
+  within 30 days. In some cases this may not be possible, for example when the
+  vulnerability exists at the protocol level and the industry must coordinate on
+  the disclosure process.
+* If a CVE number is required, one will be requested from [MITRE][mitre]
+  providing you with full credit for the discovery.
+* We will decide on a planned release date and let you know when it is.
+* Prior to release, we will inform major dependents that a security-related
+  patch is impending.
+* Once the fix has been released we will publish a security advisory on GitHub
+  and in the Server → Security Updates category on the [Swift forums][swift-forums-sec].
+
+[sswg]: https://github.com/swift-server/sswg
+[sswg-security]: https://github.com/swift-server/sswg/blob/main/security/README.md
+[swift-forums-sec]: https://forums.swift.org/c/server/security-updates/
+[mitre]: https://cveform.mitre.org/

readme.md

@@ -355,3 +355,7 @@ Lambda functions performance is usually measured across two axes:
 Larger packages size (Zip file uploaded to AWS Lambda) negatively impact the cold start time, since AWS needs to download and unpack the package before starting the process.
 
 Swift provides great Unicode support via [ICU](http://site.icu-project.org/home). Therefore, Swift-based Lambda functions include the ICU libraries which tend to be large. This impacts the download time mentioned above and an area for further optimization. Some of the alternatives worth exploring are using the system ICU that comes with Amazon Linux (albeit older than the one Swift ships with) or working to remove the ICU dependency altogether. We welcome ideas and contributions to this end.
+
+## Security
+
+Please see [SECURITY.md](SECURITY.md) for details on the security process.