Add Roadie/Backstage docs

[samnixon87]

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• [xcal] I have followed the repository's pull request submission guidelines
• I have updated my user documentation
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• New integration for Backstage. Uses an LD API token to authenticate calls in order to retrieve feature flags.

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[InTheCloudDan]

@samnixon87 There's one more issue with the run and it doesn't look like I have permissions to push to your branch for this PR. Can you fix the end-of-file for the horizontal.svg

Fix End of Files.........................................................Failed
- hook id: end-of-file-fixer
- duration: 0.08s
- exit code: 1
- files were modified by this hook

Fixing integrations/roadie/assets/images/horizontal.svg

[InTheCloudDan]

See comment above in PR

[samnixon87]

@samnixon87 There's one more issue with the run and it doesn't look like I have permissions to push to your branch for this PR. Can you fix the end-of-file for the horizontal.svg

Just pushed a change @InTheCloudDan and the EOL error on the horizontal svg looks like it's been resolved. 👍