Adding some documentation

Reviewing if the merging indicated in #1822 is possible, but well, it
is not, because they target a different set of files. It might still
be interesting to unify all these tests, and create a set of
extensions as well as regexes or tests they should meet. But not for
the time being.
So it closes #1822.

Author: JJ

xt/perl-nbsp.t

@@ -5,6 +5,12 @@ use Test;
 use lib 'lib';
 use Test-Files;
 
+=begin overview
+
+Insure any text that mentions Perl uses a no-break space after it. 
+
+=end overview
+
 my @files = Test-Files.files.grep({$_.ends-with: '.pod6'|'.md'});
 
 plan +@files;

xt/trailing-whitespace.t

@@ -5,6 +5,12 @@ use Test;
 use lib 'lib';
 use Test-Files;
 
+=begin overview
+
+Make sure that no line includes trailing whitespace.
+
+=end overview
+
 my @files = Test-Files.files\
     .grep({$_ ne 'LICENSE'})\
     .grep({! $_.contains: 'custom-theme'})\