Add Dockerfile & ghcr container build workflow

[spwoodcock]

• I wanted to give Obj2Tiles a whirl to convert ODM .obj --> 3d tiles (to view in a browser).
• In order to do so, and without installing dotnet on my machine, I decided to create a Dockerfile and build a container image.
• I have tested the image locally and it works.
• Also added a ghcr publishing workflow that will build a :master tagged image on each push, in addition to tagged :v1.4.0 tag when a new tag is pushed.

[HeDo88TH]

Thanks for the PR, I will review it asap.
Btw we have got binary releases for every operating system/arch so you don't actually need to have dotnet installed to run obj2tiles 👍

[Copilot]

Pull request overview

Adds containerization support for Obj2Tiles so the CLI can be run without installing .NET locally, and introduces a GitHub Actions workflow to build/push a multi-arch image to GHCR on pushes/tags.

Changes:

• Add a multi-stage Dockerfile that publishes a self-contained (single-file, trimmed) Obj2Tiles binary and runs it in a minimal runtime image.
• Add a GitHub Actions workflow to build and push linux/amd64 + linux/arm64 images to GHCR using Buildx with GHA caching.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
Dockerfile	Builds and publishes the Obj2Tiles CLI into a container image.
.github/workflows/image.yml	Builds/pushes a multi-arch GHCR image on pushes to master and on tags.

[spwoodcock]

Thanks for the PR, I will review it asap. Btw we have got binary releases for every operating system/arch so you don't actually need to have dotnet installed to run obj2tiles 👍

Ah of course, thanks!

Still, I'm planning on running this in an automated way to generate 3d tiles, and would orchestrate the generation via container Jobs in Kubernetes. A container image would be super helpful 😄

Copilot actually suggested 3 reasonable things - fixing