fix(deps): update dependency katex to v0.16.21 [security] (#668)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

package.json

@@ -2,7 +2,7 @@
     "name": "structurizr-site-generatr",
     "dependencies": {
         "bulma": "1.0.3",
-        "katex": "0.16.19",
+        "katex": "0.16.21",
         "lunr": "2.3.9",
         "lunr-languages": "1.14.0",
         "mermaid": "11.4.1",