unit-case
Specify lowercase or uppercase for units.
    a { width: 10px; }
/**              ↑
 *     These units */
The fix option can automatically fix most of the problems reported by this rule.
Options
string: "lower"|"upper"
"lower"
The following patterns are considered problems:
a {
  width: 10PX;
}
a {
  width: 10Px;
}
a {
  width: 10pX;
}
a {
  width: 10PIXEL;
}
a {
  width: calc(10PX * 2);
}
The following patterns are not considered problems:
a {
  width: 10px;
}
a {
  width: calc(10px * 2);
}
"upper"
The following patterns are considered problems:
a {
  width: 10px;
}
a {
  width: 10Px;
}
a {
  width: 10pX;
}
a {
  width: 10pixel;
}
a {
  width: calc(10px * 2);
}
The following patterns are not considered problems:
a {
  width: 10PX;
}
a {
  width: calc(10PX * 2);
}