Fixes in 1993/leo

Running 'make' now links 'mind' to 'leo' (via the 'mind' rule).

Format/typo check the README.md file.

This should complete the entry unless a certain thing I found is a bug
in which case the bugs.md has to be updated (and the README.md refer to
it). This is not certain yet.

1993/leo/Makefile

@@ -111,7 +111,7 @@ PROG= ${ENTRY}
 #
 OBJ= ${PROG}.o
 DATA=
-TARGET= ${PROG}
+TARGET= ${PROG} mind
 #
 ALT_OBJ=
 ALT_TARGET= mind