[librsvg/wip/dimensions-api: 5/11] Briefly document each LengthUnit

[Federico Mena Quintero <federico src gnome org>]

commit e5ed1ee5a3ae43d12b819dbb3a71a30483616190
Author: Federico Mena Quintero <federico gnome org>
Date:   Wed Feb 6 17:06:42 2019 -0600

    Briefly document each LengthUnit

 rsvg_internals/src/length.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/rsvg_internals/src/length.rs b/rsvg_internals/src/length.rs
index 8b076a2d..d54b7583 100644
--- a/rsvg_internals/src/length.rs
+++ b/rsvg_internals/src/length.rs
@@ -7,12 +7,22 @@ use parsers::Parse;
 use parsers::ParseError;
 use properties::ComputedValues;
 
+/// Units for length values
 #[derive(Debug, PartialEq, Copy, Clone)]
 pub enum LengthUnit {
+    /// `1.0` means 100%
     Percent,
+
+    /// Pixels, or the CSS default unit
     Px,
+
+    /// Size of the current font
     Em,
+
+    /// x-height of the current font
     Ex,
+
+    /// Inches
     In,
 }