Bump to 1.10.0

This version:
  - Fixes Matrix-to-Slack image upload
  - No longer sends markdown-formatted @-mention links in the plaintext
    body of Matrix events; instead uses plaintext username the way
    text-only clients traditionally have it.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "matrix-puppet-slack",
-  "version": "1.9.0",
+  "version": "1.10.0",
   "description": "",
   "main": "index.js",
   "scripts": {