Set inject default extname from file's extname

[jiangtj]

PR Checklist

• The commit message follows our guidelines.
• Tests for the changes was maked (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs in NexT website have been added / updated (for features).

PR Type

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

If there is no extension, will add .swig.

What is the new behavior?

If there is no extension, will add file's extname or .swig.

e.g. use md extname https://gitlab.com/JiangTJ/next-test/blob/master/scripts/fix-scheme.js#L15-17

Does this PR introduce a breaking change?

• Yes.
• No.

[ivan-nginx]

Here is an overview of what got changed by this pull request:

Complexity decreasing per file
==============================
+ scripts/events/lib/injects.js  -1
         

See the complete overview on Codacy