Build for Windows, MacOs and Linux (#11)

* macosx build
* update to .net8 and newest nugets
* added context menu to file list
* update version number

Assets/favicon_io/about.txt

@@ -0,0 +1,6 @@
+This favicon was generated using the following font:
+
+- Font Title: Genos
+- Font Author: Copyright 2011 The Genos Project Authors (https://github.com/googlefonts/genos)
+- Font Source: http://fonts.gstatic.com/s/genos/v12/SlGNmQqPqpUOYTYjacb0Hc91fTwVA0_orUK6K7ZsAg.ttf
+- Font License: SIL Open Font License, 1.1 (http://scripts.sil.org/OFL))

Assets/favicon_io/site.webmanifest

@@ -0,0 +1 @@
+{"name":"","short_name":"","icons":[{"src":"/android-chrome-192x192.png","sizes":"192x192","type":"image/png"},{"src":"/android-chrome-512x512.png","sizes":"512x512","type":"image/png"}],"theme_color":"#ffffff","background_color":"#ffffff","display":"standalone"}