fix: upgrade multiple dependencies with Snyk

Snyk has created this PR to upgrade:
  - gatsby-source-filesystem from 2.3.10 to 2.11.1.
    See this package in npm: https://www.npmjs.com/package/gatsby-source-filesystem
  - gatsby-transformer-remark from 2.8.14 to 2.16.1.
    See this package in npm: https://www.npmjs.com/package/gatsby-transformer-remark

See this project in Snyk:
https://app.snyk.io/org/killshot13/project/7566b9be-c2cc-48f2-9c2d-b3be8b6ef90f?utm_source=github&utm_medium=upgrade-pr

package.json

@@ -25,8 +25,8 @@
 		"gatsby-plugin-advanced-sitemap": "^1.6.0",
 		"gatsby-plugin-react-helmet": "^3.3.3",
 		"gatsby-plugin-sass": "^2.8.0",
-		"gatsby-source-filesystem": "2.3.10",
-		"gatsby-transformer-remark": "2.8.14",
+		"gatsby-source-filesystem": "2.11.1",
+		"gatsby-transformer-remark": "2.16.1",
 		"js-yaml": "^3.12.2",
 		"lodash": "^4.17.21",
 		"marked": "^0.7.0",