fix giphy padding

lib/src/giphy_attachment.dart

@@ -97,7 +97,7 @@ class GiphyAttachment extends StatelessWidget {
                     top: 0,
                     child: Container(
                       decoration: BoxDecoration(
-                          color: Colors.white,
+                          color: Colors.transparent,
                           borderRadius: BorderRadius.only(
                             bottomRight: Radius.circular(16.0),
                           )),
@@ -133,8 +133,6 @@ class GiphyAttachment extends StatelessWidget {
               if (attachment.title != null)
                 Container(
                   alignment: Alignment.bottomCenter,
-                  child: Material(
-                    color: Colors.white,
                   child: Row(
                     mainAxisAlignment: MainAxisAlignment.spaceBetween,
                     children: [
@@ -181,7 +179,6 @@ class GiphyAttachment extends StatelessWidget {
                     ],
                   ),
                 ),
-                ),
               SizedBox(
                 height: 4.0,
               ),
@@ -317,7 +314,10 @@ class GiphyAttachment extends StatelessWidget {
             ),
           ),
           Padding(
-            padding: const EdgeInsets.only(top: 8.0),
+            padding: const EdgeInsets.only(
+              top: 8.0,
+              bottom: 8,
+            ),
             child: Row(
               children: [
                 Row(