build: Add Makefile with utilities for creating posts and diagrams

[agrski]

Why

Motivation

From my experiences in #40, it was somewhat involved to create and run the appropriate commands for generating images from Mermaid diagrams, particularly when considering the inclusion of copyright notices for each image. Regenerating these was also somewhat annoying, with the steps needing to be performed in the right order -- regenerating via mmdc didn't include the copyright notice, and re-running convert would add an additional such notice (thereby duplicating it).

In short, this process was ideal for automation. Makefiles are a convenient way of defining reusable recipes, especially when there are files in nested directories, regular transformations of file names, and multiple files which may need to be reprocessed. Makefiles have the further benefit that only out of date files need to be reprocessed, which is faster and more efficient, particularly when there are many such files in existence.

In addition, posts and Mermaid diagrams all have some level of boilerplate common to each of them. For posts, this is simply the front matter, whereas for diagrams it is not only the front matter but also definitions for styling classes of entities. Rather than having to copy & paste this from existing diagrams, it is convenient to be able to generate these from pre-defined templates, in the process creating files with the appropriate names.

Issues

• Fixes Add Makefile recipe for templating Mermaid diagrams #41
• Fixes Add Makefile recipe for generating PNGs from Mermaid diagrams #42

What

Changes

• Add Makefile at the project root.
• Add Make recipe for listing available commands/targets.
• Add Make recipe for creating new draft posts.
• Add Make recipe for creating new Mermaid diagrams for draft posts.
• Add Make recipe for (re)generating images from Mermaid diagrams.

Testing

This has been tested with some of the files from #40.