Add utility function to split string into css value and unit.

dj_iconify/util.py

+import re
+
+
+def split_css_unit(string: str):
+    """Split string into value and unit.
+    
+    >>> split_css_unit("12px")
+    (12, 'px')
+    >>> split_css_unit("1.5em")
+    (1.5, 'em')
+    >>> split_css_unit("18%")
+    (18, '%')
+    >>> split_css_unit("200")
+    (200, '')
+    """
+    _value = re.findall("^[0-9.]+", string)
+    value = float(_value[0]) if "." in _value[0] else int(_value[0])
+    unit = string[len(_value[0]):]
+
+    return value, unit