Add documentation links and deployment effect

- Add API documentation links to all Cargo.toml files
- Add API documentation links to all crate READMEs
- Add API Reference link to main README
- Add Hercules CI effect to push docs to gh-pages on main branch

dev/flake-module.nix

@@ -1,5 +1,6 @@
 {
   inputs,
+  withSystem,
   ...
 }:
 {
@@ -218,9 +219,24 @@
       };
     };
   herculesCI =
-    { ... }:
+    hci@{ lib, ... }:
     {
       ciSystems = [ "x86_64-linux" ];
+      onPush.default.outputs = {
+        effects.pushDocs = lib.optionalAttrs (hci.config.repo.branch == "main") (
+          withSystem "x86_64-linux" (
+            { config, hci-effects, ... }:
+            hci-effects.gitWriteBranch {
+              git.checkout.remote.url = hci.config.repo.remoteHttpUrl;
+              git.checkout.forgeType = "github";
+              git.checkout.user = "x-access-token";
+              git.update.branch = "gh-pages";
+              contents = config.packages.docs;
+              destination = "development"; # directory
+            }
+          )
+        );
+      };
     };
   hercules-ci.flake-update = {
     enable = true;