chore: drop Node.js 18

[stevenjoezhang]

What does it do?

Versions of Node.js prior than 18 are already in End-Of-Life status. We should upgrade the supported Node.js versions in package.json. The required Node.js versions for other Hexo plugins also need to be upgraded accordingly.
Besides, require(esm) is now enabled by default since Node.js 20.19.0

Screenshots

Pull request tasks

• Add test cases for the changes.
• Passed the CI test.

[github-actions]

How to test

git clone -b node https://github.com/hexojs/hexo.git
cd hexo
npm install
npm test

[coveralls]

Pull Request Test Coverage Report for Build 16492920209

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall first build on node at 99.526%

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Totals
Change from base Build 15609358336:	99.5%
Covered Lines:	9859
Relevant Lines:	9906

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💛 - Coveralls

[Copilot]

Pull Request Overview

This pull request updates the minimum Node.js version requirement from 18 to 20.19.0, removing support for Node.js 18 which has reached End-Of-Life status. The change also adds support for Node.js 24 in CI workflows.

• Updates minimum Node.js version requirement to 20.19.0 in package.json
• Updates CI workflows to test against Node.js versions 20, 22, and 24 instead of 18, 20, and 22
• Aligns with Node.js lifecycle and enables require(esm) functionality available by default in Node.js 20.19.0+

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
package.json	Updates engines.node requirement from ">=18" to ">=20.19.0"
.github/workflows/tester.yml	Updates CI matrix to test Node.js versions 20, 22, 24
.github/workflows/benchmark.yml	Updates benchmark workflows to use Node.js versions 20, 22, 24