finished ch20 intro

.obsidian/workspace.json

@@ -63,6 +63,20 @@
               "title": "Advanced Features"
             }
           },
+          {
+            "id": "8cdde5c4be386d20",
+            "type": "leaf",
+            "state": {
+              "type": "markdown",
+              "state": {
+                "file": "Unsafe Rust.md",
+                "mode": "source",
+                "source": false
+              },
+              "icon": "lucide-file",
+              "title": "Unsafe Rust"
+            }
+          },
           {
             "id": "78cd7043d5d51ffa",
             "type": "leaf",
@@ -116,7 +130,7 @@
             }
           }
         ],
-        "currentTab": 3
+        "currentTab": 4
       }
     ],
     "direction": "vertical"
@@ -259,10 +273,11 @@
       "command-palette:Open command palette": false
     }
   },
-  "active": "de2ac5df5b921166",
+  "active": "8cdde5c4be386d20",
   "lastOpenFiles": [
-    "Pattern Matching.md",
     "Advanced Features.md",
+    "Unsafe Rust.md",
+    "Pattern Matching.md",
     "Places Patterns Can Be Used.md",
     "Pattern Syntax.md",
     "Refutability.md",
@@ -286,7 +301,6 @@
     "Leaky Reference Cycles.md",
     "Test Controls.md",
     "Ref Cell Mutability.md",
-    "Reference Counter Smart Pointer.md",
     "minigrep/src/lib.rs",
     "does_not_compile.svg",
     "Untitled.canvas",