Update markdown-it-mark requirement from ^2.0.0 to ^3.0.0 (#87)

Updates the requirements on [markdown-it-mark](https://github.com/markdown-it/markdown-it-mark) to permit the latest version.
- [Release notes](https://github.com/markdown-it/markdown-it-mark/releases)
- [Changelog](https://github.com/markdown-it/markdown-it-mark/blob/master/CHANGELOG.md)
- [Commits](markdown-it/markdown-it-mark@2.0.0...3.0.0)

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

package.json

@@ -41,7 +41,7 @@
     "markdown-it-emoji": "^1.4.0",
     "markdown-it-footnote": "^3.0.1",
     "markdown-it-ins": "^3.0.0",
-    "markdown-it-mark": "^2.0.0",
+    "markdown-it-mark": "^3.0.0",
     "markdown-it-sub": "^1.0.0",
     "markdown-it-sup": "^1.0.0",
     "sluggo": "^0.2.0"