Added a GitHub Codespaces configuration. (#3966)

.devcontainer/Dockerfile

@@ -0,0 +1,5 @@
+FROM mcr.microsoft.com/devcontainers/base:debian
+
+RUN apt-get update && apt-get -y install --no-install-recommends \
+  build-essential cmake cmake-curses-gui doxygen git graphviz \
+  less libtool-bin libyajl-dev mpi-default-dev valgrind wget

.devcontainer/devcontainer.json

@@ -0,0 +1,26 @@
+{
+  "name": "HDF5 Developer",
+  "build": {
+    "context": "..",
+    "dockerfile": "Dockerfile"
+  },
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "ms-python.python",
+        "ms-toolsai.jupyter",
+        "ms-vscode.cpptools",
+        "ms-vscode.live-server",
+        "ms-vscode-remote.remote-containers",
+        "ms-azuretools.vscode-docker",
+        "h5web.vscode-h5web",
+        "davidanson.vscode-markdownlint"
+      ],
+      "settings": {
+        "C_Cpp.default.cppStandard": "c++17",
+        "C_Cpp.default.cStandard": "c99",
+        "terminal.integrated.shell.linux": "/bin/bash"
+      }
+    }
+  }
+}

.devcontainer/noop.txt

@@ -0,0 +1,3 @@
+This file is copied into the container along with environment.yml* from the
+parent folder. This file prevents the Dockerfile COPY instruction from failing
+if no environment.yml is found.