build(deps-dev): Bump the flex-development group with 1 update (#403)

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

Author: dependabot[bot]

package.json

@@ -97,7 +97,7 @@
     "@flex-development/docast": "1.0.0-alpha.13",
     "@flex-development/docast-parse": "1.0.0-alpha.5",
     "@flex-development/esm-types": "2.0.0",
-    "@flex-development/mkbuild": "1.0.0-alpha.20",
+    "@flex-development/mkbuild": "1.0.0-alpha.21",
     "@graphql-eslint/eslint-plugin": "3.20.1",
     "@sindresorhus/slugify": "2.2.1",
     "@types/chai": "4.3.5",