LibWeb: Handle steps(x, start) like steps(x, jump-start)

Author: https://github.com/Gingeh
Commit: cd5d8f4d95
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2173
Reviewed-by: https://github.com/AtkinsSJ ✅

Userland/Libraries/LibWeb/CSS/StyleValues/EasingStyleValue.cpp

@@ -342,7 +342,7 @@ double EasingStyleValue::Steps::evaluate_at(double input_progress, bool before_f
     //    - jump-start,
     //    - jump-both,
     //    increment current step by one.
-    if (position == Steps::Position::JumpStart || position == Steps::Position::JumpBoth)
+    if (position == Steps::Position::JumpStart || position == Steps::Position::Start || position == Steps::Position::JumpBoth)
         current_step += 1;
 
     // 3. If both of the following conditions are true: