Bump lodash from 4.17.15 to 4.17.21

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.15 to 4.17.21.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.15...4.17.21)

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

Author: dependabot[bot]

package-lock.json

@@ -208,7 +208,7 @@
 		"jquery": "^3.5.0",
 		"js-sequence-diagrams": "git+https://github.com/Moeditor/js-sequence-diagrams.git",
 		"katex": "^0.10.2",
-		"lodash": "^4.17.15",
+		"lodash": "^4.17.21",
 		"mermaid": "^8.4.8",
 		"mini-css-extract-plugin": "^0.8.0",
 		"mocha": "^6.1.4",