fix(snyk): Upgrade bootstrap and generate .snyk file

.snyk

@@ -0,0 +1,9 @@
+# Snyk (https://snyk.io) policy file, patches or ignores known vulnerabilities.
+version: v1.13.3
+# ignores vulnerabilities until expiry date; change duration by modifying expiry date
+ignore:
+  'npm:mem:20180117':
+    - showdown > yargs > os-locale > mem:
+        reason: None given
+        expires: '2019-04-01T10:08:52.588Z'
+patch: {}

package.json

@@ -20,7 +20,7 @@
   "dependencies": {
     "ace-builds": "^1.4.1",
     "awesomplete": "^1.1.2",
-    "bootstrap": "^4.2.1",
+    "bootstrap": "^4.3.1",
     "cookie": "^0.3.1",
     "express": "^4.16.2",
     "frappe-datatable": "^1.8.0",

yarn.lock

@@ -457,10 +457,10 @@ 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@^4.2.1:
-  version "4.2.1"
-  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-4.2.1.tgz#8f8bdca024dbf0e8644da32e918c8a03a90a5757"
-  integrity sha512-tt/7vIv3Gm2mnd/WeDx36nfGGHleil0Wg8IeB7eMrVkY0fZ5iTaBisSh8oNANc2IBsCc6vCgCNTIM/IEN0+50Q==
+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"