customize manifest to show splash screen as needed

Author: CGJennings

manifest.mf

@@ -1,3 +1,2 @@
 Manifest-Version: 1.0
-X-COMMENT: Main-Class will be added automatically by build
-
+SplashScreen-Image: resources/splash.png

nbproject/project.properties

@@ -7,6 +7,7 @@ application.homepage=https://cgjennings.ca/projects/checker/
 application.splash=
 application.title=librivox_checker
 application.vendor=Christopher G. Jennings
+auxiliary.org-netbeans-spi-editor-hints-projects.perProjectHintSettingsFile=nbproject/cfg_hints.xml
 build.classes.dir=${build.dir}/classes
 build.classes.excludes=**/*.java,**/*.form
 # This directory is removed when the project is cleaned:
@@ -44,7 +45,7 @@ javac.classpath=\
     ${file.reference.flatlaf-1.1.2.jar}
 # Space-separated list of extra javac options
 javac.compilerargs=
-javac.deprecation=false
+javac.deprecation=true
 javac.external.vm=true
 javac.modulepath=
 javac.processormodulepath=
@@ -98,13 +99,10 @@ manifest.file=manifest.mf
 meta.inf.dir=${src.dir}/META-INF
 mkdist.disabled=false
 platform.active=default_platform
+project.license=mit
 run.classpath=\
     ${javac.classpath}:\
     ${build.classes.dir}
-# Space-separated list of JVM arguments used when running the project.
-# You may also define separate properties like run-sys-prop.name=value instead of -Dname=value.
-# To set system properties for unit tests define test-sys-prop.name=value:
-run.jvmargs=
 run.modulepath=\
     ${javac.modulepath}
 run.test.classpath=\