docs: port inches and cm to readthedocs

docs/dsl/cm.rst

@@ -1,2 +1,19 @@
 cm
 --
+
+Given centimeters, returns the number of pixels according to the deck's DPI.
+
+Parameters
+^^^^^^^^^^
+
+n
+  the number of centimeters
+
+
+Examples
+^^^^^^^^
+
+.. code-block:: ruby
+
+  cm(1)         # 118.11px (for default Deck::dpi of 300)
+  cm(2) + cm(1) # 354.33ox (for default Deck::dpi of 300)

docs/dsl/inches.rst

@@ -1,2 +1,19 @@
 inches
 ------
+
+Given inches, returns the number of pixels according to the deck's DPI.
+
+Parameters
+^^^^^^^^^^
+
+n
+  the number of inches
+
+
+Examples
+^^^^^^^^
+
+.. code-block:: ruby
+
+  inches(2.5)                # 750 (for default Deck::dpi of 300)
+  inches(2.5) + inches(0.5)  # 900 (for default Deck::dpi of 300)