update readmes and package descriptions

plugins/positioner/Cargo.toml

@@ -1,6 +1,7 @@
 [package]
 name = "tauri-plugin-positioner"
 version = "0.2.7"
+description = "Position your windows at well-known locations."
 authors.workspace = true
 license.workspace = true
 edition.workspace = true

plugins/positioner/package.json

@@ -1,6 +1,7 @@
 {
   "name": "tauri-plugin-positioner-api",
   "version": "0.0.0",
+  "description": "Position your windows at well-known locations.",
   "license": "MIT or APACHE-2.0",
   "authors": [
     "Tauri Programme within The Commons Conservancy"