Use SVG badge

[hugovk]

Description

Use SVG Crowdin badge instead of PNG, for visual consistency with others.

Also add some missing fullstops, and because there's just one option under "Install Magento", there's no need to say "see either".

Manual testing scenarios

1. Visit the README in the PR
2. Check the badge and text is improved

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• [n/a] All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

Before

After

[magento-cicd2]

All committers have signed the CLA.

[naydav]

Hi @hugovk,
This repository is related to the GraphQL project
Could you close this PR and create a new one (from the same branch) to https://github.com/magento/magento2/pulls
Thanks

[hugovk]

@naydav Hi, I've already made a similar PR to https://github.com/magento/magento2/, please see magento/magento2#18439.

Is it so that when that is merged, the README in this repo will also get updated? Thanks.

[naydav]

@hugovk,
Yes, after merging magento/magento2#18439 this repo will be automatically updated
Thanks for the contribution!