More consistent app name use in the README file

[antononcube]

I think the following README lines "raku" should be replaced with "Raku":

$ raku foo --files-only  # look for "foo", only produce filenames

$ raku foo --before=2 --after=2  # also produce 2 lines before and after

$ raku '{.contains("foo") && .contains("bar")}'  # lines with foo AND bar

I.e. the lines above should be:

$ rak foo --files-only  # look for "foo", only produce filenames

$ rak foo --before=2 --after=2  # also produce 2 lines before and after

$ rak '{.contains("foo") && .contains("bar")}'  # lines with foo AND bar

[lizmat]

Thanks. Fixed in the next release