MySinglePageAppWebPart.manifest.json

{
  "$schema": "https://developer.microsoft.com/json-schemas/spfx/client-side-web-part-manifest.schema.json",
  "id": "85c66304-0802-417a-a753-de96fea19565",
  "alias": "MySinglePageAppWebPart",
  "componentType": "WebPart",

  // The "*" signifies that the version should be taken from the package.json
  "version": "*",
  "manifestVersion": 2,

  // If true, the component can only be installed on sites where Custom Script is allowed.
  // Components that allow authors to embed arbitrary script code should set this to true.
  // https://support.office.com/en-us/article/Turn-scripting-capabilities-on-or-off-1f2c515f-5d7e-448a-9fd7-835da935584f
  "requiresCustomScript": false,
  "hiddenFromToolbox": true,
  "supportedHosts": ["SharePointWebPart"],

  "preconfiguredEntries": [{
    "groupId": "5c03119e-3074-46fd-976b-c60198311f70", // Other
    "group": { "default": "Other" },
    "title": { "default": "MySPA" },
    "description": { "default": "A Single Page Application developed with SPFx" },
    "officeFabricIconFontName": "Page",
    "properties": {
      "description": "Hello dear user"
    }
  }]
}