chore: improve documentation

* GPG walkthrough
* many minor improvements

docs/content/en/docs/_index.md

@@ -3,4 +3,3 @@ title: "PIV Agent Documentation"
 ---
 
 PIV Agent must be installed and set up to work with your hardware security device before use.
-See below for instructions.

docs/content/en/docs/faq.md

@@ -0,0 +1,30 @@
+---
+title: "FAQ"
+weight: 40
+---
+
+## How do I switch between gpg-agent and piv-agent
+
+### Linux (systemd)
+
+Stop both `gpg-agent` and `piv-agent`:
+
+{{% alert title="Note" %}}
+The `pkill` is required because `gpg` may be configured to automatically start `gpg-agent` in a manner which is not managed by `systemd`.
+{{% /alert %}}
+
+```
+systemctl --user stop gpg-agent.socket gpg-agent.service piv-agent.socket piv-agent.service; pkill gpg-agent
+```
+
+Start `piv-agent`:
+
+```
+systemctl --user start piv-agent.socket
+```
+
+Or start `gpg-agent`:
+
+```
+systemctl --user start gpg-agent.socket
+```