feat: Add presence heartbeat for Matrix online status

- matrix-gateway: POST /internal/matrix/presence/online endpoint
- usePresenceHeartbeat hook with activity tracking
- Auto away after 5 min inactivity
- Offline on page close/visibility change
- Integrated in MatrixChatRoom component

node_modules/camelcase-css/README.md

@@ -0,0 +1,27 @@
+# camelcase-css [![NPM Version][npm-image]][npm-url] [![Build Status][travis-image]][travis-url]
+
+> Convert a kebab-cased CSS property into a camelCased DOM property.
+
+
+## Installation
+[Node.js](http://nodejs.org/) `>= 6` is required. Type this at the command line:
+```shell
+npm install camelcase-css
+```
+
+
+## Usage
+```js
+const camelCaseCSS = require('camelcase-css');
+
+camelCaseCSS('-webkit-border-radius');  //-> WebkitBorderRadius
+camelCaseCSS('-moz-border-radius');     //-> MozBorderRadius
+camelCaseCSS('-ms-border-radius');      //-> msBorderRadius
+camelCaseCSS('border-radius');          //-> borderRadius
+```
+
+
+[npm-image]: https://img.shields.io/npm/v/camelcase-css.svg
+[npm-url]: https://npmjs.org/package/camelcase-css
+[travis-image]: https://img.shields.io/travis/stevenvachon/camelcase-css.svg
+[travis-url]: https://travis-ci.org/stevenvachon/camelcase-css