Supported for VuePress 2.0.0-beta.40 or later

Usage of plugin is changed since VuePress 2.0.0-beta.40.
See also VuePress change logs

This version is supported the breaking changes.
If you use version 1.0.4 or earlier, please check README.md

• Merge pull request #2 from monsat/fix-vuepress-update 0bb17aa
• docs: update for version 1.0.5 3004552
• fix: param is not required cdb401a
• refactor: import plugin file c50060f
• feat: update VuePress version 6ab38f5

v1.0.4...v1.0.5