Document universal block opener

Author: Sainan

docs/QoL Improvements/Universal Block Opener.md

@@ -0,0 +1,23 @@
+Pluto allows `do` to be used as a universal block opener, meaning it can be used instead of `then` and `begin`.
+```pluto title="If Statement Example"
+local x = 3
+if x == 3 do
+    print("x is 3!")
+end
+```
+```pluto title="Class Statement Example"
+class Human do
+    function __construct(public name) end
+    function greet() print($"Hello, {self.name}!") end
+end
+new Human("John"):greet()
+```
+```pluto title="Enum Statement Example"
+enum Suit do
+    HEARTS,
+    DIAMONDS,
+    CLUBS,
+    SPADES
+end
+assert(HEARTS == 1)
+```