Create or source missing image files from documentation

[Yantrio]

Some mdx files are missing images, we should source or create images to replace them.

[Yantrio]

So far I've identified 3 missing images:

graph-example.png

Usage: https://github.com/opentffoundation/opentf/blob/a83e5ee5ac71c35886044d22ecf8e6d63e019016/website/docs/cli/commands/graph.mdx#L56C46-L56C46

Description:
A screenshot of an svg generated by the command opentf graph | dot -Tsvg > graph.svg

intro-opentf-apis.png

Usage: https://github.com/opentffoundation/opentf/blob/a83e5ee5ac71c35886044d22ecf8e6d63e019016/website/docs/intro/index.mdx#L16

Description
A small image showing how opentf, providers and the "target API" all work together.

In text form:
OpenTF <--> Terraform Provider <--> Target API

intro-opentf-workflow.png

Usage: https://github.com/opentffoundation/opentf/blob/a83e5ee5ac71c35886044d22ecf8e6d63e019016/website/docs/intro/index.mdx#L26

Description: An image displaying the workflow steps of writing IaC with opentf.

Write -> Plan -> Apply
With some text describing each of the phases, and what they include.

[damianstasik]

@Yantrio do you think some of these images can be skipped?