docs: request_body Caddyfile directive (#104)

* Add documentation about request_body directive in Caddyfile

* Add note about matchers support

Co-authored-by: Francis Lavoie <lavofr@gmail.com>

* Improve description of max_size parameter

Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

* Improve text

Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

* Improve description of request_body directive

Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

Co-authored-by: Francis Lavoie <lavofr@gmail.com>
Co-authored-by: Matt Holt <mholt@users.noreply.github.com>

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

@@ -0,0 +1,29 @@
+---
+title: request_body (Caddyfile directive)
+---
+
+# request_body
+
+Manipulates or sets restrictions on the bodies of incoming requests.
+
+
+## Syntax
+
+```caddy-d
+request_body [<matcher>] {
+  max_size <value>
+}
+```
+
+- **max_size** is the maximum size in bytes allowed for the request body. It accepts all formats supported by [go-humanize](https://github.com/dustin/go-humanize/blob/master/bytes.go).
+
+
+## Examples
+
+Limit request body sizes to 10 megabytes:
+
+```caddy-d
+request_body {
+  max_size 10MB
+}
+```