Check link isExternal before adding target="_blank" (#1211)

Paul Trotter

2024-06-17 42640bceb57c450d5c2427bd2b449827468d0ede

 quartz/plugins/transformers/frontmatter.ts

@@ -90,6 +90,7 @@
        description: string
        publish: boolean
        draft: boolean
        lang: string
        enableToc: string
        cssclasses: string[]
      }>