Add LICENSE

LICENSE

+Copyright 2023 Autistici/Inventati <info@autistici.org>
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+“Software”), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR
+THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+

README.md

@@ -8,3 +8,11 @@ identifying metadata.
 Meant to be used in combination with
 [wp-mat-server](https://git.autistici.org/noblogs/wp-mat-server), a
 simple API wrapper for mat2.
+
+### Configuration
+
+Define these in wp-config.php to control the plugin behavior:
+
+* `WP_MAT_ENDPOINT` - full URL to the *wp-mat-server* instance to use
+  (including the */api/cleanup* path).
+