upx: add page (#1921)

pages/common/upx.md

@@ -0,0 +1,15 @@
+# upx
+
+> Compress or decompress executables.
+
+- Compress executable:
+
+`upx {{file}}`
+
+- Decompress executable:
+
+`upx -d {{file}}`
+
+- Detailed help:
+
+`upx --help`