units: move to common directory (#5647)

pages/common/units.md

@@ -0,0 +1,32 @@
+# units
+
+> Provide the conversion between two units of measure.
+> More information: <https://www.gnu.org/software/units/>.
+
+- Run in interactive mode:
+
+`units`
+
+- List all units containing a specific string in interactive mode:
+
+`search {{string}}`
+
+- Show the conversion between two simple units:
+
+`units {{quarts}} {{tablespoons}}`
+
+- Convert between units with quantities:
+
+`units "{{15 pounds}}" {{kilograms}}`
+
+- Show the conversion between two compound units:
+
+`units "{{meters / second}}" "{{inches / hour}}"`
+
+- Show the conversion between units with different dimensions:
+
+`units "{{acres}}" "{{ft^2}}"`
+
+- Show the conversion of byte multipliers:
+
+`units "{{15 megabytes}}" {{bytes}}`