jarsigner: add page (#3547)

pages/common/jarsigner.md

@@ -0,0 +1,16 @@
+# jarsigner
+
+> Sign and verify Java Archive (JAR) files.
+> More information: <https://docs.oracle.com/javase/9/tools/jarsigner.htm>.
+
+- Sign a JAR file:
+
+`jarsigner {{path/to/file.jar}} {{keystore_alias}}`
+
+- Sign a JAR file with a specific algorithm:
+
+`jarsigner -sigalg {{algorithm}} {{path/to/file.jar}} {{keystore_alias}}`
+
+- Verify the signature of a JAR file:
+
+`jarsigner -verify {{path/to/file.jar}}`