chore(marketplace): update readme (#1614)

* chore(marketplace): update readme

Signed-off-by: Nick Boldt <[email protected]>

* Ben says we can remove the sheet link entirely

Signed-off-by: Nick Boldt <[email protected]>

---------

Signed-off-by: Nick Boldt <[email protected]>

Author: nickboldt

catalog-entities/marketplace/README.md

@@ -1,9 +1,13 @@
 # Creating & Editing Extension Catalog Plugins
 
-Spreadsheet for tracking the work is here: https://docs.google.com/spreadsheets/d/1K_LqKYma9nRM5teKD-uCnbB3qKC8Hk2E5jvcpMSfjTs/edit?gid=771893283#gid=771893283
-
 ## Working with Plugin Folders & Files
 
+Packages are not located in this file tree, but are instead co-located under the `workspaces/*/metadata/` folders. 
+
+Content will be merged from those folders into this folder when reassembling the complete marketplace entities in the plugin catalog index image. 
+
+The latest of these index images will be published to quay. For example, see https://quay.io/rhdh/plugin-catalog-index
+
 Below are some practical instructions that might help you in the process of creating and updating plugins and packages for use in the RHDH Extensions catalog plugin.
 
 ## `packages/`