Docs: Add scale query string parameter to share panel (#24599)

Document the new scale query string parameter introduced in #23625.

Co-authored-by: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

docs/sources/reference/share_panel.md

@@ -27,6 +27,7 @@ https://play.grafana.org/d/000000012/grafana-play-home?orgId=1&from=156871968017
 - **height**: height in pixels. Default is 400.
 - **tz**: timezone in the format `UTC%2BHH%3AMM` where HH and MM are offset in hours and minutes after UTC
 - **timeout**: number of seconds. The timeout can be increased if the query for the panel needs more than the default 30 seconds.
+- **scale**: numeric value to configure device scale factor. Default is 1. Use a higher value to produce more detailed images (higher DPI). Supported in Grafana v7.0+.
 
 ## Embed Panel