fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-INFLIGHT-6095116

package.json

@@ -6,7 +6,7 @@
   "dependencies": {
     "core-js": "^2.6.0",
     "disqus-react": "^1.0.4",
-    "gatsby": "^2.0.0",
+    "gatsby": "^4.10.2",
     "gatsby-image": "^2.0.22",
     "gatsby-link": "^2.0.7",
     "gatsby-plugin-canonical-urls": "^2.0.8",
@@ -15,7 +15,7 @@
     "gatsby-plugin-offline": "^2.0.5",
     "gatsby-plugin-react-helmet": "^3.0.0",
     "gatsby-plugin-sass": "^2.0.1",
-    "gatsby-plugin-sharp": "^2.0.15",
+    "gatsby-plugin-sharp": "^4.22.0",
     "gatsby-plugin-sitemap": "^2.0.3",
     "gatsby-plugin-yandex-metrika": "^1.0.5",
     "gatsby-remark-copy-linked-files": "^2.0.7",
@@ -24,7 +24,7 @@
     "gatsby-transformer-remark": "^2.1.15",
     "gatsby-transformer-sharp": "^2.1.9",
     "lodash": "^4.17.4",
-    "node-sass": "^4.9.3",
+    "node-sass": "^7.0.2",
     "prop-types": "^15.6.1",
     "react": "^16.5.1",
     "react-disqus-comments": "^1.1.1",
@@ -53,13 +53,13 @@
     "deploy": "gatsby build --prefix-paths && gh-pages -d public"
   },
   "devDependencies": {
-    "eslint": "^5.10.0",
+    "eslint": "^6.0.0",
     "eslint-config-airbnb": "^17.1.0",
     "eslint-plugin-import": "^2.9.0",
     "eslint-plugin-jsx-a11y": "^6.0.3",
     "eslint-plugin-react": "^7.7.0",
     "gatsby-plugin-styled-jsx": "^3.0.3",
-    "stylelint": "^9.1.1",
+    "stylelint": "^13.0.0",
     "stylelint-config-standard": "^18.2.0",
     "prettier": "^1.14.2"
   }