Use file-saver to export accounts (#701)

* use file-saver

* bring back the fake implementation

* we never know

* fix background test

yarn.lock

@@ -2150,6 +2150,7 @@ __metadata:
     "@types/bn.js": ^4.11.6
     "@types/enzyme": ^3.10.8
     "@types/enzyme-adapter-react-16": ^1.0.6
+    "@types/file-saver": ^2.0.2
     "@types/react-copy-to-clipboard": ^5.0.0
     "@types/react-dom": ^17.0.3
     "@types/react-router": ^5.1.13
@@ -2159,6 +2160,7 @@ __metadata:
     "@wojtekmaj/enzyme-adapter-react-17": ^0.6.0
     enzyme: ^3.11.0
     enzyme-adapter-react-16: ^1.15.6
+    file-saver: ^2.0.5
     i18next: ^19.9.2
     react: ^17.0.2
     react-dom: ^17.0.2
@@ -2787,6 +2789,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@types/file-saver@npm:^2.0.2":
+  version: 2.0.2
+  resolution: "@types/file-saver@npm:2.0.2"
+  checksum: ccdfbbe45c68b54192d1a9fb9c5f7594c7eabe64ad55982839f0e758b72a62ae0e2edcee16af2b7c197d53f57047b5e11dac5d7805326718d0cb5a5e2f4dc382
+  languageName: node
+  linkType: hard
+
 "@types/filesystem@npm:*":
   version: 0.0.29
   resolution: "@types/filesystem@npm:0.0.29"
@@ -7611,6 +7620,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"file-saver@npm:^2.0.5":
+  version: 2.0.5
+  resolution: "file-saver@npm:2.0.5"
+  checksum: 0f835236534377c9b7591b995d94ae5061166452fb1f784548b706ff48984930e45a7947cfe393ce86b84ef2ec89064120c5d5ab5186146c508bb022c71ced3d
+  languageName: node
+  linkType: hard
+
 "file-selector@npm:^0.2.2":
   version: 0.2.4
   resolution: "file-selector@npm:0.2.4"