Add Not and Inv instructions to spec

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

vm.md

@@ -74,6 +74,19 @@ wrapping around to 0.
 * Or
     * **Params**: REG1, REG2
     * `REG1 = REG1 | REG2`
+* Inv
+    * **Params**: REG1
+    * `REG1 = ~REG1`
+* Not
+    * **Params**: REG1
+    * ```
+    if REG1 == 0 {
+        REG1 = 0;
+    } else {
+        REG1 = 1;
+    }
+    ```
+    * Boolean NOT; equivalent of C's `!` unary operator
 * Xor
     * **Params**: REG1, REG2
     * `REG1 = REG1 ^ REG2`