Docs: Missing Installation guides

[rajitha1998]

Expected Behavior

• The install guidelines and Introduction docs should be loaded correctly

  Actual Behavior

• Some pages related to a first-time contributor is not working.

Steps to Reproduce the Problem

1. Visit: Contributing page
2. Try navigating to install guides, Getting Started with Knative Serving or Getting Started With Eventing.

Additional Info

[mattmoor]

Indeed, those are all broken 😬

[mattmoor]

I believe that's from here, and the links work in markdown form, so something we need to fix: https://github.com/knative/docs/blob/master/CONTRIBUTING.md#getting-started

/kind good-first-issue

[abrennan89]

/assign shuheiktgw

[knative-prow-robot]

@abrennan89: GitHub didn't allow me to assign the following users: shuheiktgw.

Note that only knative members, repo collaborators and people who have commented on this issue/PR can be assigned. Additionally, issues/PRs can only have 10 assignees at the same time.
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In response to this:

/assign shuheiktgw

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