update the top level documentation files

- README has been added
- CHANGELOG/package.json have been changed to alpha release

packages/plugins/Measure/CHANGELOG.md

@@ -1,9 +1,5 @@
 # CHANGELOG
 
-## unpublished
+## 1.0.0-alpha.0
 
-- Initial release.
-
-## 1.0.0
-
-Initial release.
+Alpha release. This tool is ready for use in minimal clients or for expert users. For caveats, see the README file.

packages/plugins/Measure/README.md

@@ -0,0 +1,13 @@
+# Measure
+
+## Scope
+
+The tool offers measuring distances and areas as multi-point lines and polygons.
+
+## Configuration
+
+There are currently no configurable parameters to this plugin. It always offers modes (Select/Draw/Edit/Delete), a switch to measure either distances or areas, a unit selection (m/km), and an RGB colour selection for text and lines displayed regarding measurements.
+
+## Caveats
+
+The tool is not yet configurable and may yield unexpected behaviour when used in combination with the plugins Draw and Pins, as some interactions do overlap. The colouring tool requires a basic understanding of RGB colour mixing. You can easily offer this tool to expert users, but it may confuse regular users.

packages/plugins/Measure/package.json

@@ -1,6 +1,6 @@
 {
     "name": "@polar/plugin-measure",
-    "version": "1.0.0",
+    "version": "1.0.0-alpha.0",
     "description": "Plugin Measure",
     "license": "EUPL-1.2",
     "type": "module",