Add project import to the existing welcome to GitLab page
## Problem
Currently, when a new user signs up, they may not be aware that we offer the ability to import existing projects from other services. The public projects can always be found when creating a project but they do not align with our goal of influencing free to paid conversion.
## Solution
We should replace the existing `Explore public projects` with an option to `Import a project` this will allow new users immediately after sign up to know that we support imports.
The final solution should utilize the same module as the existing `Explore public projects` we should replace it with the following:
Import a project
Import from GitHub, Bitbucket, Google, Fogbugz, Gitea, Repo by URL, Manifest file, GitLab export
As seen in this mockup

## ICE score
| Impact | Confidence | Effort | Score |
| ------ | ------ | ------ | ------ |
| 6 | 5 | 9 | 6.67 |
issue