RFR: Copy images to dist directory on build

[Iris Clark]

On Tue, 1 Aug 2023 18:23:12 GMT, calnan <duke at openjdk.org> wrote:

> Updates to the Makefile to copy across any image files into the build/dist directory so that the images appear when the index.html file is viewed.

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/guide/pull/111#pullrequestreview-1557615267