Move code rendering to the backend & frontend improvements (#176)

Added Chroma & Goldmark

Added Mermaidjs

More languages supported

Add default values for gist links input

Added copy code from markdown blocks

package.json

@@ -20,9 +20,7 @@
     "codemirror": "^6.0.1",
     "cssnano": "^5.1.15",
     "dayjs": "^1.11.9",
-    "github-markdown-css": "^5.2.0",
-    "highlight.js": "^11.7.0",
-    "markdown-it": "^13.0.1",
+    "github-markdown-css": "^5.5.0",
     "nodemon": "^2.0.22",
     "postcss": "^8.4.13",
     "postcss-cssnext": "^3.1.1",