Add link to liberapay in about screen

briar-desktop/src/main/kotlin/org/briarproject/briar/desktop/Strings.kt

@@ -27,4 +27,5 @@ object Strings {
     const val LICENSE = "GNU Affero General Public License v3"
     const val WEBSITE = "https://briarproject.org"
     const val EMAIL = "desktop@briarproject.org"
+    const val LIBERAPAY = "https://liberapay.com/Briar/"
 }

briar-desktop/src/main/kotlin/org/briarproject/briar/desktop/ui/AboutScreen.kt

@@ -129,6 +129,7 @@ private fun GeneralInfo() {
         add(Entry("Commit time", DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss").format(commitTime))) // NON-NLS
         add(Entry(i18n("about.website"), Strings.WEBSITE, true))
         add(Entry(i18n("about.contact"), Strings.EMAIL, true))
+        add(Entry(i18n("about.liberapay"), Strings.LIBERAPAY, true))
     }
 
     VerticallyScrollableArea { scrollState ->

briar-desktop/src/main/resources/strings/BriarDesktop.properties

@@ -336,6 +336,7 @@ about.version=Version
 about.version.core=Briar Core Version
 about.contact=Contact
 about.website=Website
+about.liberapay=Liberapay
 
 # Mailbox
 mailbox.setup.intro.title=Mailbox