The work of highlighting the source code based on the file extension is delegated to the pygments library. It seems that they don't support those extensions:
>>> from pygments.lexers import get_lexer_by_name
>>> get_lexer_by_name('py')
<pygments.lexers.PythonLexer>
>>> get_lexer_by_name('js')
<pygments.lexers.JavascriptLexer>
>>> get_lexer_by_name('jsx')
Traceback (most recent call last):
...
pygments.util.ClassNotFound: no lexer for alias 'jsx' found
>>> get_lexer_by_name('txs')
Traceback (most recent call last):
...
pygments.util.ClassNotFound: no lexer for alias 'txs' found
The work of highlighting the source code based on the file extension is delegated to the pygments library. It seems that they don't support those extensions:
You could request that enhancement to them: https://github.com/pygments/pygments/issues