Add detail to negation docs

I felt the negation docs didn't cover checking if a value was *not* another value and didn't point out that `not` can't be combined with other operators.

[ci skip]

docs/en/02_Developer_Guides/01_Templates/01_Syntax.md

@@ -178,7 +178,7 @@ Conditionals can also provide the `else` case.
 
 ### Negation
 
-The inverse of `<% if %>` is `<% if not %>`.
+You can check if a variable is false with `<% if not %>`.
 
 ```ss
 <% if not $DinnerInOven %>
@@ -186,6 +186,17 @@ The inverse of `<% if %>` is `<% if not %>`.
 <% end_if %>
 ```
 
+Note that you cannot combine this with other operators such as `==`.
+
+
+For more nuanced check you can use the `!` operator.
+
+```ss
+<% if $MyDinner != "quiche" %>
+    Lets go out
+<% end_if %>
+```
+
 ### Boolean Logic
 
 Multiple checks can be done using `||`, `or`, `&&` or `and`.