add 100ms duration (#1149)

Author: lukasoppermann

.changeset/nervous-icons-relate.md

@@ -0,0 +1,5 @@
+---
+'@primer/primitives': patch
+---
+
+Add 100ms duration for very short transitions

src/tokens/base/motion/timing.json5

@@ -9,6 +9,10 @@
         $value: '75ms',
         $type: 'duration',
       },
+      '100': {
+        $value: '100ms',
+        $type: 'duration',
+      },
       '200': {
         $value: '200ms',
         $type: 'duration',