Add fallback rule to Text for numerical extensions heuristic

[DecimalTurn]

Description

As discussed in #7656, I'm adding an explicit fallback for numerical extensions since they should be treated as generic.

Checklist:

• I am fixing a misclassified language
  • I have included new sample [fixtures] for the misclassified language:
    • Source(s):
      • https://github.com/pyenv/pyenv/blob/master/plugins/python-build/share/python-build/2.1.3 (MIT)
      • https://github.com/GangZhuo/BaiduPCS/blob/master/autom4te.cache/output.2 (MIT)
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

[lildude]

LGTM. Thanks.

Important

The changes in this PR will not appear on GitHub until the next release has been made and deployed. See here for more details.