Add some examples for this tool. Be aware that I did not add any examples for
`-l` since I can not grasp how it really works. For example, imagine a file like
this:
```
A B
B C
C A
A D
D E
E F
F A
```
This is what we show without -l:
```
tsort: cycle in data
tsort: A
tsort: D
tsort: E
tsort: F
F
tsort: cycle in data
tsort: A
tsort: B
tsort: C
C
A
D
B
E
```
and with -l:
```
tsort: cycle in data
tsort: A
tsort: D
tsort: E
tsort: F
F
tsort: cycle in data
tsort: A
tsort: B
tsort: C
C
A
D
B
E
```
Compare this with the output of OpenBSD 6.7 for the same file.
Without -l:
```
tsort: cycle in data
tsort: A
tsort: D
tsort: E
tsort: F
A
B
C
D
E
F
```
and with -l:
```
tsort: cycle in data
tsort: D
tsort: E
tsort: F
tsort: A
F
tsort: cycle in data
tsort: B
tsort: C
tsort: A
A
B
C
D
E
```
I also [[https://lists.freebsd.org/pipermail/freebsd-hackers/2020-July/056336.html|asked]] @hackers but got no answer.