Use relative paths for images

[sethfischer]

Proposal

Make all image src links relative.

Justification

Using relative links allows correct rendering of a local preview. For this reason GitHub's docs recommend using relative links:

Relative links are easier for users who clone your repository. Absolute links may not work in clones of your repository - we recommend using relative links to refer to other files within your repository.

Being able to preview rendered Markdown before pushing is important as it can reduce the number of errors.

Example

In mechanical/head_assembly/README.md there is one relative link, with the remaining being absolute.

The image with the relative link displays in a local preview with the remaining absolute images being broken.

Relative link

| <img src="../../images/components/structural/S43.png" width="50%"> |
| :--: |
| Figure 1: 3D Printed Parts |

Absolute link

<img src="/images/head/finala.png" width="50%">

[sethfischer]

If this proposal is accepted I will prepare a pull request.

[ericjunkins]

Sounds good assigned it to you