ci: commitlint ignore Dependabot's commit messages

[HJunyuan]

Problem

Build fails because Commitlint says:

✖   body's lines must not be longer than 100 characters [body-max-line-length]

• chore(deps): bump jsonwebtoken and testcafe-reporter-dashboard #161
• https://circleci.com/gh/Open-Attestation/verify.gov.sg/14616

Solution

Add to Commitlint ignore when commit message is signed off by Dependabot:

// commitlint.config.js
module.exports = {
  ...,
  ignores: [(msg) => /Signed-off-by: dependabot\[bot\]/m.test(msg)],
};

Referencing from: dependabot/dependabot-core#2445 (comment)