Add descriptions for remaining pages

basics/introduction.md

@@ -1,5 +1,6 @@
 ---
 title: Introduction
+description: An overview of objects, tags, and filters in the Liquid template language.
 ---
 
 Liquid code can be categorized into [**objects**](#objects), [**tags**](#tags), and [**filters**](#filters).

basics/operators.md

@@ -1,5 +1,6 @@
 ---
 title: Operators
+description: Using operators to perform calculations in the Liquid template language.
 ---
 
 Liquid includes many logical and comparison operators.

basics/truthy-and-falsy.md

@@ -1,5 +1,6 @@
 ---
 title: Truthy and falsy
+description: An overview of boolean logic in the Liquid template language.
 ---
 
 In programming, anything that returns `true` in a conditional is called **truthy**. Anything that returns `false` in a conditional is called **falsy**. All object types can be described as either truthy or falsy.

basics/types.md

@@ -1,5 +1,6 @@
 ---
 title: Types
+description: An overview of data types in the Liquid template language.
 ---
 
 Liquid objects can have one of six types:

basics/whitespace.md

@@ -1,5 +1,6 @@
 ---
 title: Whitespace control
+description: An overview of controlling whitespace between code in the Liquid template language.
 ---
 
 In Liquid, you can include a hyphen in your tag syntax `{% raw %}{{-{% endraw %}`, `{% raw %}-}}{% endraw %}`, `{% raw %}{%-{% endraw %}`, and `{% raw %}-%}{% endraw %}` to strip whitespace from the left or right side of a rendered tag.