[Trainer] Add codemirror in new text section

[nasdan]

• Add select component to select some language: HTML, CSS, Javascript, JSX, Typescript, TSX, JSON, Bash, Markdown, YAML, diff, C# (cs)
• Add empty option.
• Create common component MarkdownEditor (codemirror)
• Add codemirror to get markdown styles.
• Only add custom styles for heading sizes.

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Languages

[nasdan]

Remove ********************************* after each new text too