Add support for using sftp-server found within PATH

Before trying list of well-known candidates allow detection routine to
check if the binary is discoverable inside PATH already. This covers
cases for unknown distributions or user built packages, which could be
symlinked into `/usr/local/bin` to be discoverable before system packages
and Windows, where needed dependencies might have different packaging.

Signed-off-by: Arthur Sengileyev <arthur.sengileyev@gmail.com>

Author: arixmkii

pkg/reversesshfs/reversesshfs.go

@@ -63,6 +63,9 @@ func (rsf *ReverseSSHFS) Prepare() error {
 }
 
 func DetectOpensshSftpServerBinary() string {
+	if exe, err := exec.LookPath("sftp-server"); err == nil {
+		return exe
+	}
 	homebrewSSHD := []string{
 		"/usr/local/sbin/sshd",
 		"/opt/homebrew/sbin/sshd",