Bump bootstrap from 4.1.3 to 4.3.1 in /app (#16)

Bumps [bootstrap](https://github.com/twbs/bootstrap) from 4.1.3 to 4.3.1.
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](twbs/bootstrap@v4.1.3...v4.3.1)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

app/package.json

@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "bootstrap": "4.1.3",
+    "bootstrap": "4.3.1",
     "react": "^16.6.0",
     "react-cookie": "3.0.4",
     "react-dom": "^16.6.0",

app/yarn.lock

@@ -1711,10 +1711,10 @@ boolbase@^1.0.0, boolbase@~1.0.0:
   resolved "https://registry.yarnpkg.com/boolbase/-/boolbase-1.0.0.tgz#68dff5fbe60c51eb37725ea9e3ed310dcc1e776e"
   integrity sha1-aN/1++YMUes3cl6p4+0xDcwed24=
 
-bootstrap@4.1.3:
-  version "4.1.3"
-  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-4.1.3.tgz#0eb371af2c8448e8c210411d0cb824a6409a12be"
-  integrity sha512-rDFIzgXcof0jDyjNosjv4Sno77X4KuPeFxG2XZZv1/Kc8DRVGVADdoQyyOVDwPqL36DDmtCQbrpMCqvpPLJQ0w==
+bootstrap@4.3.1:
+  version "4.3.1"
+  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-4.3.1.tgz#280ca8f610504d99d7b6b4bfc4b68cec601704ac"
+  integrity sha512-rXqOmH1VilAt2DyPzluTi2blhk17bO7ef+zLLPlWvG494pDxcM234pJ8wTc/6R40UWizAIIMgxjvxZg5kmsbag==
 
 brace-expansion@^1.1.7:
   version "1.1.11"