Add dev container (#86)

* Add dev container

* Update contributing.md with container info

* Reduce container size a bit

Don't install "recommended" packages through `apt`. Also install `make` since it is recommended by `cmake`.

---------

Co-authored-by: alexander-novo <alexander-novo@users.noreply.github.com>

Author: alexander-novo

.devcontainer/Dockerfile

@@ -0,0 +1,31 @@
+FROM ubuntu:24.04
+
+RUN apt update -y && apt install -y --no-install-recommends\
+	gcc \
+	g++ \
+	make \
+	cmake \
+	ninja-build \
+	git \
+	ca-certificates \
+	libopenblas-dev \
+	&& apt clean && rm -rf /var/lib/apt/lists/*
+
+# Install SuiteSparse for klu
+RUN git clone --single-branch --depth 1 --branch v7.10.2 https://github.com/DrTimothyAldenDavis/SuiteSparse.git /tmp/suitesparse && \
+	cd /tmp/suitesparse && \
+	mkdir -p build && cd build && \
+	cmake -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+		-DSUITESPARSE_ENABLE_PROJECTS="klu" .. && \
+	ninja install && \
+	rm -rf /tmp/suitesparse
+
+# Install sundials using klu from previous step
+RUN git clone --single-branch --branch develop https://github.com/LLNL/sundials.git /tmp/sundials && \
+	cd /tmp/sundials && \
+	git checkout 07d21c2c5ae33211a9a2fafd8eac56de5582dce0 && \
+	mkdir -p build && cd build && \
+	cmake -G Ninja -DCMAKE_BUILD_TYPE=RelWithDebInfo \
+		-DENABLE_KLU=ON .. && \
+	ninja install && \
+	rm -rf /tmp/sundials

.devcontainer/devcontainer.json

@@ -0,0 +1,12 @@
+{
+	"build": {
+		"dockerfile": "Dockerfile"
+	},
+	"customizations": {
+		"vscode": {
+			"extensions": [
+				"ms-vscode.cpptools"
+			]
+		}
+	}
+}

CONTRIBUTING.md

@@ -457,3 +457,7 @@ class Matrix   // No, class is outside GridKit namespace
 {
   // matrix code
 };
+```
+
+## Development Container
+A development container is available for all developers using VS Code to develop. This will automatically install all pre-requisite software you need to develop in GridKit. Any developer who wishes to use this setup can follow [this tutorial](https://code.visualstudio.com/docs/devcontainers/tutorial) and simply use the option "Reopen Folder in Container" rather than "New Dev Container...", which will automatically build the included container.