adds PercentInput for value modding in sell action

lootalot_front/src/components/PercentInput.vue

@@ -0,0 +1,28 @@
+<template>
+        <div class="field has-addons">
+          <div v-show="is_opened" class="control has-icons-left">
+            <input class="input is-small" type="number" size="3" min=-50 max=50 step=5>
+            <span class="icon is-small is-left">
+              <i class="fas fa-percent"></i>
+            </span>
+          </div>
+          <div class="control">
+            <button class="button is-small is-outlined"
+              @click="is_opened = !is_opened"
+            >
+              <small v-if="!is_opened">Mod.</small>
+              <span v-else class="icon"><i class="fas fa-times-circle"></i></span>
+            </button>
+          </div>
+        </div>
+</template>
+
+<script>
+    export default {
+        data () {
+            return {
+                is_opened: false,
+            };
+        }
+    }
+</script>