update README

README.md

@@ -16,3 +16,73 @@ a pinned item to unpin it. The pinned items cache is shared with `nwg-menu` and
 ![screenshot-01.png](https://scrot.cloud/images/2021/05/30/screenshot-01.png)
 
 [more screenshots](https://scrot.cloud/album/nwg-drawer.Bogd)
+
+## Installation
+
+### Dependencies
+
+- go 1.16 (just to build)
+- gtk3
+- gtk-layer-shell
+
+Optional (recommended):
+
+- thunar
+- alacritty
+
+You may use another file manager and terminal emulator (see command line arguments), but for now the program has
+ only been tested with the two mentioned above.
+
+### Steps
+
+1. Clone the repository, cd into it.
+2. Install necessary golang libraries with `make get`.
+3. `make build`
+4. `sudo make install`
+
+Building the gotk3 library takes quite a lot of time. If your machine is x86_64, you may skip steps 3-4, and
+install the provided binary by executing step 4.
+
+## Command line arguments
+
+```text
+$ nwg-drawer -h
+Usage of nwg-drawer:
+  -c uint
+    	number of Columns (default 6)
+  -fm string
+    	File Manager (default "thunar")
+  -fscol uint
+    	File Search result COLumns (default 2)
+  -fslen int
+    	File Search name length Limit (default 80)
+  -is int
+    	Icon Size (default 64)
+  -lang string
+    	force lang, e.g. "en", "pl"
+  -o string
+    	name of the Output to display the menu on (sway only)
+  -ovl
+    	use OVerLay layer
+  -s string
+    	Styling: css file name (default "drawer.css")
+  -spacing uint
+    	icon spacing (default 20)
+  -term string
+    	Terminal emulator (default "alacritty")
+  -v	display Version information
+  ```
+
+## Styling
+
+Edit `~/.config/nwg-panel/drawer.css` to your taste.
+
+## Credits
+
+This program uses some great libraries:
+
+- [gotk3](https://github.com/gotk3/gotk3) Copyright (c) 2013-2014 Conformal Systems LLC,
+Copyright (c) 2015-2018 gotk3 contributors
+- [gotk3-layershell](https://github.com/dlasky/gotk3-layershell) by [@dlasky](https://github.com/dlasky/gotk3-layershell/commits?author=dlasky) - many thanks for writing this software, and for patience with my requests!
+- [go-sway](https://github.com/joshuarubin/go-sway) Copyright (c) 2019 Joshua Rubin
+- [go-singleinstance](github.com/allan-simon/go-singleinstance) Copyright (c) 2015 Allan Simon