Publish extension as NPM package

When creating and publishing an extension for vue3-openlayers, you should follow this instruction. This assures, the lib can be found easily and that it follows a common plugin naming pattern.

• The package name should be vue3-openlayers-<plugin>-<feature>, e. g. vue3-openlayers-source-foo
• Please add the keywords vue3-openlayers-extension and openlayers to your published package

{
  "name": "vue3-openlayers-source-foo",
  "keywords": [
    "openlayers",
    "vue3-openlayers",
  ],
  //...
}