Vertical stepper design

[obulat]

Fixes #57

Description

This PR has three main goals:

1. Implement the mockups of the design by Francisco with Vertical stepper and a Recommended license card on the right.
2. Move state management to Vuex for easier handling of the app-wide state.
3. Update the language, using the language approved by the CC team.

Other information

Checklist:

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the master branch of the repository.
• My commit messages follow best practices.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no
  visible errors.

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[akmadian]

• Step one title changes from "Do you know which license you need?" to "License Expertise" when advanced to step 2. I think it would be best to keep it as "Do you know which license you need?" for consistency.

• Would be good to add cursor: pointer on step headers to show that they are clickable

• Odd stepper behavior with ND licenses

  • Select "I know which license I need"
  • Select any license with ND
  • Select next
  • See behavior

• A little thing, unrelated to the PR: the .env file in the repo's root contains stuff that is duplicated in the vue.config.js. Is it necessary to have .env?

[akmadian]

Also would be good to add "fixes #57" in the PR body

[obulat]

• Step one title changes from "Do you know which license you need?" to "License Expertise" when advanced to step 2. I think it would be best to keep it as "Do you know which license you need?" for consistency.
  This was the approved wording from the spreadsheet.

• Would be good to add cursor: pointer on step headers to show that they are clickable
  Added.

• Odd stepper behavior with ND licenses

  • Select "I know which license I need"
  • Select any license with ND
  • Select next
  • See behavior
    I've updated the method for setting visible/enabled steps which solved this problem.

• A little thing, unrelated to the PR: the .env file in the repo's root contains stuff that is duplicated in the vue.config.js. Is it necessary to have .env?
  I'm not sure about that, these files were added automatically by vue-cli when it added i18n. Will need to look into it.

[akmadian]

Looks great! I got pretty nit-picky again, but again, I think it's getting to be necessary at this point. Please address the comments and ask questions if needed :) I assumed you were ready for another review because you added a commit called "Build the site" and replied to my comments.

[akmadian]

Looks great! One small thing, and I think we should be ready to merge :)

[akmadian]

This issue should be fixed before merge because it could potentially cause legal issues if the license deeds are inaccessible based on how we provide the information.

[akmadian]

Looks great! I'm approving, but please do these two things before merging:

• Change the site title in ./public/index.html from "Creative Commons License Chooser" to "Choose a License"
• Please add a link to this repo in the footer, maybe something like "Contribute on GitHub." After "Icons by Noun Project"

Great work, I'm really excited about this :)