The manifest file is a JSON file that describes various properties of the plugin. If you use the Yeoman generator, it should be automatically generated based on the answers you've provided. The supported properties are:
`manifest_version` | number | **Yes** | For now should always be "1".
`name` | string | **Yes** | Name of the plugin. Should be a user-friendly string, as it will be displayed in the UI.
`version` | string | **Yes** | Version number such as "1.0.0".
`app_min_version` | string | **Yes** | Minimum version of Joplin that the plugin is compatible with. In general it should be whatever version you are using to develop the plugin.
`description` | string | No | Detailed description of the plugin.