Added videos to SD Connect Beta pages

[mkannisto]

Proposed changes

I've added instructional videos to the new SD Connect Beta pages:

• Transfer: https://csc-guide-preview.rahtiapp.fi/origin/mk-sdconnectbeta/data/sensitive-data/sd-connect-share-tranfer-data/
• Collaborate: https://csc-guide-preview.rahtiapp.fi/origin/mk-sdconnectbeta/data/sensitive-data/sd-connect-share-workspace/

Checklist before requesting a review

• I have followed the instructions in the Contributing and Styleguide documents.
• My pull request passes the automated tests. If not, visit pull requests at Travis CI and have a look at the job log.
• I have included a link to the appropriate preview page (select your branch from the list).