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GH-37051: [Dev][JS] Add Dependabot configuration for npm (#37053)

### Rationale for this change

We can add `MINOR: [JS] ` prefix to PRs from Dependabot automatically.

### What changes are included in this PR?

Add a configuration for npm.

### Are these changes tested?

No. I want to test this by merging this to main.

### Are there any user-facing changes?

No.
* Closes: #37051

Lead-authored-by: Sutou Kouhei <kou@clear-code.com>
Co-authored-by: Sutou Kouhei <kou@cozmixng.org>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>