Merge branch 'ordering_publication_external' into 'develop'

Adding ordering for publication section external

See merge request R3/howto-cards!351

external/publication/10WaysImproveEnglish/10WaysImproveEnglish.md

 ---
+order: 900
 layout: page
 permalink: /external/publication/10WaysImproveEnglish/
 shortcut: publication:10WaysImproveEnglish

external/publication/add-gitignore/add-gitignore.md

 ---
+order: 700
 layout: page
 permalink: /external/publication/add-gitignore/
 shortcut: publication:add-gitignore

external/publication/publish-repo/publish-repo.md

 ---
+order: 600
 layout: page
 permalink: /external/publication/publish-repo/
 shortcut: publication:publish-repo

external/publication/publishInBiotools/publishInBiotools.md

 ---
+order: 800
 layout: page
 permalink: /external/publication/publishInBiotools/
 shortcut: publication:publishInBiotools