DOCS: Added boolean expressions and TODO items.

TODO.md

@@ -1,8 +1,18 @@
 # Major Planned Features
 
-## Boolean operations and type
+## Compile Errors as expression
 
-* contains (for lists or strings)
+## String handling
+
+Mostly handled by ranges and indexing for strings?
+
+Type comparisons?
+
+```
+let foo = "foo";
+foo is str; // evaluates to true
+foo is int; // evaluates to false
+```
 
 ## Query Language (Experimental)
 

docsite/site/content/reference/expressions.md

@@ -144,6 +144,16 @@ let lst = [1, "two", {three = 3}];
 {three = 3, two = 2} in lst // evaluates to false
 ```
 
+### Boolean Operators
+
+UCG has the standard boolean operators: `&&` and `||`. Both of them short circuit and they require the expressions on each
+side to be boolean.
+
+```
+true && false == false;
+false || true == true;
+```
+
 #### Operator Precedence
 
 UCG binary operators follow the typical operator precedence for math. `*` and