Base: Document open(1)

Author: https://github.com/bugaevc
Commit: https://github.com/SerenityOS/serenity/commit/15daf88e930
Pull-request: https://github.com/SerenityOS/serenity/pull/1866

Base/usr/share/man/man1/open.md

@@ -0,0 +1,22 @@
+## Name
+
+open - open file or URL
+
+## Synopsis
+
+```**sh
+$ open <file-or-url...>
+```
+
+## Description
+
+Open the given file(s), or the given URL(s), in the standard viewer for that
+kind of file. For non-file URLs, open the URL in the Browser.
+
+## Examples
+
+```sh
+$ open http://serenityos.org http://example.org
+$ open /proc
+$ open /etc/fstab
+```