Include a profile icon for the launcher json (#6222)

build.gradle

@@ -13,6 +13,8 @@ buildscript {
 }
 import groovy.json.JsonSlurper
 import groovy.json.JsonBuilder
+
+import java.nio.file.Files
 import java.text.SimpleDateFormat
 import java.util.Date
 import java.util.LinkedHashMap
@@ -773,6 +775,7 @@ project(':forge') {
                 spec: 0,
                 profile: project.name,
                 version: launcherJson.id,
+                icon: "data:image/png;base64," + new String(Base64.getEncoder().encode(Files.readAllBytes(rootProject.file("icon.ico").toPath()))),
                 json: '/version.json',
                 path: "${project.group}:${project.name}:${project.version}",
                 logo: '/big_logo.png',