Bump lodash from 4.17.19 to 4.17.21

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.19 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.19...4.17.21)

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

package.json

@@ -33,7 +33,7 @@
     "gatsby-source-filesystem": "^1.5.8",
     "gatsby-transformer-remark": "^1.7.26",
     "gatsby-transformer-sharp": "^1.6.14",
-    "lodash": "^4.17.19",
+    "lodash": "^4.17.21",
     "prettier": "^1.8.2",
     "react-responsive-grid": "^0.3.4",
     "react-twitter-widgets": "^1.7.1",

yarn.lock

@@ -6094,9 +6094,9 @@ lodash@3.10.1:
   version "3.10.1"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-3.10.1.tgz#5bf45e8e49ba4189e17d482789dfd15bd140b7b6"
 
-lodash@4, lodash@^4.0.0, lodash@^4.1.0, lodash@^4.13.1, lodash@^4.14.0, lodash@^4.15.0, lodash@^4.17.19, lodash@^4.17.2, lodash@^4.17.4, lodash@^4.2.0, lodash@^4.2.1, lodash@^4.3.0, lodash@^4.6.1, lodash@~4.17.4:
-  version "4.17.19"
-  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.19.tgz#e48ddedbe30b3321783c5b4301fbd353bc1e4a4b"
+lodash@4, lodash@^4.0.0, lodash@^4.1.0, lodash@^4.13.1, lodash@^4.14.0, lodash@^4.15.0, lodash@^4.17.2, lodash@^4.17.21, lodash@^4.17.4, lodash@^4.2.0, lodash@^4.2.1, lodash@^4.3.0, lodash@^4.6.1, lodash@~4.17.4:
+  version "4.17.21"
+  resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.21.tgz#679591c564c3bffaae8454cf0b3df370c3d6911c"
 
 lodash@4.11.1:
   version "4.11.1"