guides: add connector stub

Author: seanmonstar

_data/stable.yml

@@ -16,14 +16,12 @@
   guides:
   - hello-world
   - echo
-  - graceful-shutdown
 
 - title: Client
   path: "/client"
   guides:
   - basic
-  - advanced
-  - configuration
+  - connectors
 
 - title: Upgrading
   path: "/upgrading"

_stable/client/connectors.md

@@ -0,0 +1,35 @@
+---
+title: Connectors, Pools, and HTTPS
+layout: guide
+---
+
+> **Unstable**: The code discussed in this guide is in `hyper-util`,
+> which is not as stable as that which is in `hyper`. It is production
+> ready, but changes may come more frequently.
+
+_TODO_
+
+## What is a connector?
+
+_TODO_
+
+## Connection Pools
+
+_TODO_
+
+## HTTPS
+
+hyper allows you to bring your own IO, so it can work on top of any TLS
+implementation. (TODO: link to runtime guide)
+
+There are also crates that provide "connectors" which result in
+easy-to-use HTTPS for the legacy client in `hyper-util`. Each has their
+own reason for existing, and pros and cons, but this list is provided to
+help you get started[^tls-list]:
+
+- [hyper-tls](https://crates.io/crates/hyper-tls)
+- [hyper-rustls](https://crates.io/crates/hyper-rustls)
+- [hyper-openssl](https://crates.io/crates/hyper-openssl)
+
+[^tls-list]: This isn't an endorsement for any of the crates, and they
+  all are maintained separately from hyper.