Add syntax highlighting

Highlighting the code based on syntax can be really useful for users as it makes it easier to read and understand code.

I came across a few plugins and resources that can help in this case:
- [flutter_highlight](https://pub.dev/packages/flutter_highlight)
- [code_text_field](https://pub.dev/packages/code_text_field)
- [creamy_field](https://pub.dev/packages/creamy_field#CreamySyntaxHighlighter)
- https://fluttergems.dev/editor-syntax-highlighter/

Review the linked flutter_highlight, code_text_field, creamy_field, and FlutterGems resources to compare syntax-highlighting options for the editor. Trace where SQL code is displayed, then define the supported syntax and verify that code is highlighted consistently in the browser-based compiler.

Written by the indexing model from the issue text.