Trim `.example` suffix when analyzing filenames

[spenserblack]

Describe the enhancement

Searching the *.example path on GitHub, I'm seeing a lot of .example files, such as:

• .env.example
• Makefile.example
• README.md.example
• *.py.example
• *.js.example

And I'm thinking that Linguist would be able to identify these files' languages correctly if it trimmed the .example suffix before checking the extension or filename. E.g.

• .env.example -> .env -> Dotenv (by filename)
• README.md.example -> README.md -> Markdown (by extension)

Does this make sense?