fix: improve .textlintignore support using linter.scanFilePath() API

[3w36zj6]

This PR is a cherry-pick of taichi/vscode-textlint#72.

.textlintignore support has broken at 8ee34bc because TextLintEngine.executeOnText() does not consider ignore file. The same goes for linter.lintText(), which was added later.

This pull request will fix .textlintignore support using linter.scanFilePath() API which was added in textlint v14.1.0. If user's textlint version is lower than v14.1.0, .textlintignore is simply ignored and other features works fine.

[3w36zj6]

I've confirmed that .textlintignore is respected in textlint@14 environments, while it's ignored in textlint@13 environments.
Could you please review this? @azu

[azu]

• Related Use new find-utils in textlint - linter.lintFile() use new find-utils textlint#1412

[azu]

LGTM