Update README.md

Author: victor-savinov

README.md

@@ -2,11 +2,27 @@
 
 ## Installation
 
-### [Chromium](https://www.chromium.org/) / [Brave](https://brave.com/) / [Vivaldi](https://vivaldi.com/) / Chrome and other
-1. Unzip all
+#### Chromium / Brave / Vivaldi / Chrome and other
+1. Download & unzip [latest release](https://github.com/victor-savinov/to-do/releases/latest)
 2. Open Extensions (*chrome://extensions/*) page in your browser
 3. Activate "Developer mode"
 4. Click on "Load unpacked" button
-5. Select "chrome" folder
+5. Select unzipped folder
 
-Or use one of the published versions: [Chrome Web Store](https://chrome.google.com/webstore/detail/to-do/mniboiicchcpkffcdlaocnkfpbdihgii)
+Or use the [published version](https://chrome.google.com/webstore/detail/mniboiicchcpkffcdlaocnkfpbdihgii/).
+
+#### Firefox / Waterfox / GNUzilla and IceCat and other
+1. Download & unzip [latest release](https://github.com/victor-savinov/to-do/releases/latest)
+2. Open Add-ons page (*about:addons*) in your browser
+3. Click on "Extensions" tab
+4. Click on "Debug Add-ons" (*about:debugging#/runtime/this-firefox*)
+5. Click on "Load Temporary Add-on…"
+6. Select "manifest.json" file from unzipped folder
+
+## Donate
+
+You can learn more on [the page](http://improvedtube.com/donate).
+
+## Credits
+
+Big thanks to all our [contributors](https://github.com/victor-savinov/to-do/graphs/contributors)!