implement upload form functions

Signed-off-by: Chloe <pinkcloudvnn@gmail.com>

lib/shopify/mutations/file.ts

@@ -0,0 +1,31 @@
+export const createStageUploads = /* GraphQL */ `
+  mutation stagedUploadsCreate($input: [StagedUploadInput!]!) {
+    stagedUploadsCreate(input: $input) {
+      stagedTargets {
+        url
+        resourceUrl
+        parameters {
+          name
+          value
+        }
+      }
+    }
+  }
+`;
+
+export const createFileMutation = /* GraphQL */ `
+  mutation fileCreate($files: [FileCreateInput!]!) {
+    fileCreate(files: $files) {
+      files {
+        fileStatus
+        ... on MediaImage {
+          id
+        }
+      }
+      userErrors {
+        field
+        message
+      }
+    }
+  }
+`;