Add .bi extension to QuickBASIC

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Description

This PR adds the .bi extension which can be interpreted as "BASIC include" file used inside certain versions of BASIC like in this case for QuickBASIC (and FreeBASIC).

Note that the estimation of the number of files is a little difficult here because the heurisitcs we used for QuickBASIC are case-sensitive, but GitHub search is case-insensitive. For that reason, I've included an upper and lower bound for the estimation of the number of files. The upper bound might include FreeBASIC files that would normally not be detected as QuickBASIC since they don't have the right casing, but it's hard to tell by how much.

Checklist:

• I am adding a new extension to a language.
  • The new extension is used in hundreds of repositories on GitHub.com
    • Search results for each extension:
      • 2k files
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • https://github.com/FellippeHeitor/InForm/blob/3820134c76970c004376cc8f92433065643966a3/InForm/InForm.bi
    • Sample license(s): MIT
  • I have included a change to the heuristics to distinguish my language from others using the same extension.

[lildude]

GitHub search is case-insensitive

You can get around this by using a regex

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Unfortunately, no.
Even with a regex, you can't get case-sensitive results.

Eg.: the following still returns lowercase results even when asking for uppercase matches: https://github.com/search?q=%2FTEST%2F&type=code

[lildude]

Even with a regex, you can't get case-sensitive results.

Sure you can: https://github.com/search?q=%2F%28%3F-i%3ATEST%29%2F&type=code

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[DecimalTurn]

I've updated the search query with the case-sensitive regex and the count is now at 2k files.