Issue #450 - Fix doc and image links

[johnwalicki]

Pull Request Template

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #450
Fixes $448

• I believe this will be the last PR related to externalLinks
• Resolves issues posted in Bug🐛: missing externalLink directives #450 (comment)

Type of change

• This change requires a documentation update

How Has This Been Tested?

Visit:

• https://open-horizon.github.io/docs/developing/container_deployment_options/ (broken link)
• https://open-horizon.github.io/docs/installing/fdo/ (missing a spacer between link and glyph)
• https://open-horizon.github.io/docs/integrating_index/ (broken link)

Checklist:

• I have tagged the reviewers in a comment below incase my pull request is ready for a review
• I have signed the commit message to agree to Developer Certificate of Origin (DCO) (to certify that you wrote or otherwise have the right to submit your contribution to the project.) by adding "--signoff" to my git commit command.

[johnwalicki]

Fixes #448 as well.

[johnwalicki]

After this PR was merged, I confirmed that the external links are now all correct.