add get_shell()

Author: scivision

+stdlib/get_shell.m

@@ -0,0 +1,7 @@
+function shell = get_shell()
+% return value of environment variable SHELL
+% this is mostly relevant on unix-like systems
+
+shell = string(getenv("SHELL"));
+
+end

+stdlib/is_wsl_path.m

@@ -1,4 +1,6 @@
 function iswsl = is_wsl_path(path)
+% heuristic to detect a WSL path
+% https://learn.microsoft.com/en-us/windows/wsl/filesystems
 arguments
   path (1,1) string {mustBeNonzeroLengthText}
 end