API 版本化迁移

[GLACIER]

添加 "ghost-api": "v2" 到 package.json 以适应新的 v2 API，否则会报错：

The {{#get}} helper requires your theme to have API access. Please enable the v2 API via your theme's package.json file. See https://docs.ghost.org/api/handlebars-themes/packagejson/"

参见：
https://docs.ghost.org/api/handlebars-themes/packagejson/
https://docs.ghost.org/faq/api-versioning/
TryGhost/Ghost#10447