Show `txt` for requirements.txt in `CodeBlock`

[ydcjeff]

Describe the bug

Currently, there is no file extension beside Copy button for requirements.txt.

Expected result

Show txt beside Copy button.

Steps to reproduce

1. Go to https://code-generator.netlify.app/create
2. Choose a template
3. See the requirements.txt in the right pane

Solution

Currently, we are using markup language from Prismjs for txt file which is not correct.

So change the language-markup to language-txt or language-text which don't exist in Prismjs languages. But this could allow us to add the file extension like here.

Another part is we are highlighting txt with markup. Since text files normally don't need syntax highlighting, we could just pass language grammar as empty object (i.e. languages['markup'] -> {}).

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[afzal442]

hi there, I would like to look into this.

/assign

[trsvchn]

@afzal442 Sure! Go for it!