docs: Add handle_errors, CEL matcher; a few other improvements

src/docs/markdown/caddyfile/directives/handle_errors.md

@@ -0,0 +1,19 @@
+---
+title: handle_errors (Caddyfile directive)
+---
+
+# handle_errors
+
+Sets up error handlers.
+
+When the normal HTTP request handlers return an error, normal procesing stops and the error handlers are invoked. Error handlers form a route which is just like normal routes, and they can do anything that normal routes can do. This enables great control and flexibility when handling errors during HTTP requests.
+
+## Syntax
+
+```
+handle_errors {
+	<directives...>
+}
+```
+
+- **<directives...>** is a list of HTTP handler directives, directive blocks, or matchers; one per line.