Fix `.btn` padding for input/button[type="image"]

Created by: WinterSilence

Description

Remove padding for input/button containing image.

Motivation & Context

Fix incorrect size of input/button: padding added to image size.

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

https://codepen.io/WinterSilence/pen/jOxdyeO?editors=1100

Related issues

scss/_buttons.scss

@@ -113,6 +113,9 @@
   }
 }
 
+[type="image"].btn {
+  padding: 0;
+}
 
 //
 // Alternate buttons

.bundlewatch.config.json

@@ -26,11 +26,11 @@
     },
     {
       "path": "./dist/css/bootstrap.css",
-      "maxSize": "29.5 kB"
+      "maxSize": "29.6 kB"
     },
     {
       "path": "./dist/css/bootstrap.min.css",
-      "maxSize": "27.5 kB"
+      "maxSize": "27.6 kB"
     },
     {
       "path": "./dist/js/bootstrap.bundle.js",