Bump underscore from 1.9.2 to 1.13.1 in /addon (#25)

Bumps [underscore](https://github.com/jashkenas/underscore) from 1.9.2 to 1.13.1.
- [Release notes](https://github.com/jashkenas/underscore/releases)
- [Commits](https://github.com/jashkenas/underscore/compare/1.9.2...1.13.1)

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

addon/package-lock.json

@@ -2574,9 +2574,9 @@
       }
     },
     "underscore": {
-      "version": "1.9.2",
-      "resolved": "https://registry.npmjs.org/underscore/-/underscore-1.9.2.tgz",
-      "integrity": "sha512-D39qtimx0c1fI3ya1Lnhk3E9nONswSKhnffBI0gME9C99fYOkNi04xs8K6pePLhvl1frbDemkaBQ5ikWllR2HQ=="
+      "version": "1.13.1",
+      "resolved": "https://registry.npmjs.org/underscore/-/underscore-1.13.1.tgz",
+      "integrity": "sha512-hzSoAVtJF+3ZtiFX0VgfFPHEDRm7Y/QPjGyNo4TVdnDTdft3tr8hEkD25a1jC+TjTuE7tkHGKkhwCgs9dgBB2g=="
     },
     "underscore-keypath": {
       "version": "0.0.22",