Test vertical-lr as well
move files to submitted directory, add file number

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rename : contributors/ttwf_tokyo/starters/css-flexbox/samples/writing-mode-stretch-ref.html => contributors/ttwf_tokyo/mittel/submitted/writing-mode-stretch-001-ref.html
rename : contributors/ttwf_tokyo/starters/css-flexbox/samples/writing-mode-stretch.html => contributors/ttwf_tokyo/mittel/submitted/writing-mode-stretch-001.html
Merge PR #19 https://github.com/w3c/csswg-test/pull/19

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rename : contributors/ttwf_tokyo/starters/css-flexbox/samples/writing-mode-stretch-ref.html => contributors/ttwf_tokyo/mittel/submitted/writing-mode-stretch-001-ref.html
rename : contributors/ttwf_tokyo/starters/css-flexbox/samples/writing-mode-stretch.html => contributors/ttwf_tokyo/mittel/submitted/writing-mode-stretch-001.html