pio-update: add page (#5520)

pages/common/pio-update.md

@@ -0,0 +1,17 @@
+# pio update
+
+> Update installed PlatformIO Core packages, development platforms and global libraries.
+> See also: `pio platform update`, `pio lib update`.
+> More information: <https://docs.platformio.org/en/latest/core/userguide/cmd_update.html>.
+
+- Perform a full update of all packages, development platforms and global libraries:
+
+`pio update`
+
+- Update core packages only (skips platforms and libraries):
+
+`pio update --core-packages`
+
+- Check for new versions of packages, platforms and libraries but do not actually update them:
+
+`pio update --dry-run`