Add double chevron icons

CHANGELOG.md

@@ -16,6 +16,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   - `arrow-up-left`
   - `arrow-up-right`
   - `cast`
+  - `chevrons-down`
+  - `chevrons-left`
+  - `chevrons-right`
+  - `chevrons-up`
   - `cloud-snow`
   - `repeat`
 </details>

icons/arrows/chevrons-down.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
+    <polyline points="7 13 12 18 17 13" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <polyline points="7 6 12 11 17 6" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+</svg>

icons/arrows/chevrons-left.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
+    <polyline points="11 17 6 12 11 7" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <polyline points="18 17 13 12 18 7" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+</svg>

icons/arrows/chevrons-right.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
+    <polyline points="13 17 18 12 13 7" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <polyline points="6 17 11 12 6 7" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+</svg>

icons/arrows/chevrons-up.svg

+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24">
+    <polyline points="17 11 12 6 7 11" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+    <polyline points="17 18 12 13 7 18" fill="none" stroke="#000" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"/>
+</svg>