readme update

Author: adamberecz

README.md

@@ -307,6 +307,31 @@ The same is true for `container`, `tag`, `options` and `option` classes.
 
 In case you need to override the same type of utility you might use [@neojp/tailwind-important-variant](https://www.npmjs.com/package/@neojp/tailwindcss-important-variant) and use eg. `bg-green-500!`.
 
+You also need to add custom background images to your `tailwind.config.js`:
+
+``` js
+const svgToDataUri = require('mini-svg-data-uri')
+
+module.exports = {
+  theme: {
+    extend: {
+      backgroundImage: (theme) => ({
+        'multiselect-caret': `url("${svgToDataUri(
+          `<svg viewBox="0 0 320 512" fill="currentColor" xmlns="http://www.w3.org/2000/svg"><path d="M31.3 192h257.3c17.8 0 26.7 21.5 14.1 34.1L174.1 354.8c-7.8 7.8-20.5 7.8-28.3 0L17.2 226.1C4.6 213.5 13.5 192 31.3 192z"></path></svg>`,
+        )}")`,
+        'multiselect-spinner': `url("${svgToDataUri(
+          `<svg viewBox="0 0 512 512" fill="${theme('colors.green.500')}" xmlns="http://www.w3.org/2000/svg"><path d="M456.433 371.72l-27.79-16.045c-7.192-4.152-10.052-13.136-6.487-20.636 25.82-54.328 23.566-118.602-6.768-171.03-30.265-52.529-84.802-86.621-144.76-91.424C262.35 71.922 256 64.953 256 56.649V24.56c0-9.31 7.916-16.609 17.204-15.96 81.795 5.717 156.412 51.902 197.611 123.408 41.301 71.385 43.99 159.096 8.042 232.792-4.082 8.369-14.361 11.575-22.424 6.92z"></path></svg>`,
+        )}")`,
+        'multiselect-remove': `url("${svgToDataUri(
+          `<svg viewBox="0 0 320 512" fill="currentColor" xmlns="http://www.w3.org/2000/svg"><path d="M207.6 256l107.72-107.72c6.23-6.23 6.23-16.34 0-22.58l-25.03-25.03c-6.23-6.23-16.34-6.23-22.58 0L160 208.4 52.28 100.68c-6.23-6.23-16.34-6.23-22.58 0L4.68 125.7c-6.23 6.23-6.23 16.34 0 22.58L112.4 256 4.68 363.72c-6.23 6.23-6.23 16.34 0 22.58l25.03 25.03c6.23 6.23 16.34 6.23 22.58 0L160 303.6l107.72 107.72c6.23 6.23 16.34 6.23 22.58 0l25.03-25.03c6.23-6.23 6.23-16.34 0-22.58L207.6 256z"></path></svg>`,
+        )}")`,
+      })
+    },
+  }
+}
+
+```
+
 ## Support
 
 Join our [Discord channel](https://discord.gg/WhX2nG6GTQ) or [open an issue](https://github.com/vueform/multiselect/issues).