Add justfile (#13189)

Author: koppor

justfile

@@ -0,0 +1,21 @@
+set windows-shell := ["powershell"]
+
+[unix]
+gui:
+    sh ./gg.cmd gradle :jabgui:run
+
+[unix]
+checkout-pr pr-id:
+    sh ./gg.cmd jbang https://github.com/JabRef/jabref/blob/main/.jbang/CheckoutPR.java {{pr-id}}
+
+[windows]
+gui:
+    .\gg.cmd gradle :jabgui:run
+
+[windows]
+checkout-pr pr-id:
+    .\gg.cmd jbang https://github.com/JabRef/jabref/blob/main/.jbang/CheckoutPR.java {{pr-id}}
+
+run-pr pr-id:
+    just checkout-pr {{pr-id}}
+    just gui