Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Previously, we did not run the workflow on push on `master` when a
release happened because the push on master is guarded by a check on
which files were changed.

With this change, I added `VERSION` to the list of files to consider
when updating `:edge`.

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>

* fix: Source `VERSION` from image ENV

Now CI builds triggered from tagged releases will always have the correct version. No need for manually updating a separate file.

* fix: Query latest GH release tag

Compare to the remote GH release tag published, rather than contents of a `VERSION` file.

`VERSION` file remains in source for now as prior releases still rely on it for an update notification.

* chore: Switch from `yq` to `jaq`

- Can more easily express a string subslice.
- Lighter weight: 9.3M vs 1.7M.
- Drawback, no YAML input/output support.

If `yq` is preferred, the `v` prefix could be removed via BASH easily enough.

* chore: Add entry to `CHANGELOG.md`

* ci: `VERSION` has no relevance to `:edge`

* docs: Update build guide + simplify `make build`

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Co-authored-by: Georg Lauterbach <44545919+georglauterbach@users.noreply.github.com>