added installation instructions

.gitignore

@@ -15,3 +15,4 @@
 # vendor/
 
 .vscode/
+fyne-cross

README.md

@@ -13,10 +13,40 @@
 - image processing backend: gift
 - cross compilation: fyne-cross
 
+## Installation
+
+Packages are currently available for Windows, macOS and Linux.
+On Windows and macOS, just download the packages from the [releases section](https://github.com/Palexer/image-viewer/releases)
+and install it as usual. 
+
+*Note for Mac users: There might be a warning, that the OS doesn't trust the application. In this case press Ctrl+left click on the
+application and select open. Next time the app should open like any other program.
+
+On Linux you'll need download the package from the [releases section](https://github.com/Palexer/image-viewer/releases) too.
+Then extract the archive.
+To install type (in the folder that contains the Makefile):
+
+``` bash
+sudo make install
+```
+
+To uninstall type:
+``` bash
+sudo make uninstall
+```
+
 ## ToDo
 
 - undo/redo: change parameter values
 - open recent images
+- creation time:
+
+```
+info, _ := os.Stat(event.Name)
+unixTime, _ := info.Sys().(*syscall.Stat_t).Ctim.Unix()
+time := time.Unix(unixTime, 0)
+log.Print(time)
+```
 
 ## License