docs: add forgotten documentation for the new openssl dependency

docs/markdown/Dependencies.md

@@ -625,6 +625,12 @@ for OpenMP support.
 
 The `language` keyword may used.
 
+## OpenSSL
+
+*(added 0.62.0)*
+
+`method` may be `auto`, `pkg-config`, `system` or `cmake`.
+
 ## pcap
 
 *(added 0.42.0)*

docs/markdown/snippets/openssl_dependency.md

@@ -0,0 +1,11 @@
+## New custom dependency for OpenSSL
+
+Detecting an OpenSSL installation in a cross-platform manner can be
+complicated. Officially, pkg-config is supported by upstream. Unofficially,
+cmake includes a FindOpenSSL using a different name and which requires
+specifying modules.
+
+Meson will now allow the pkg-config name to work in all cases using the following lookup order:
+- prefer pkg-config if at all possible
+- attempt to probe the system for the standard library naming, and retrieve the version from the headers
+- if all else fails, check if cmake can find it