Add myst config.

Result of 💾 Updating .gitignore
✅ Project already initialized with config file: myst.yml
✅ Site already initialized with config file: myst.yml.

Author: rossbar

.gitignore

@@ -189,3 +189,6 @@ cython_debug/
 
 # PyPI configuration file
 .pypirc
+
+# MyST build outputs
+_build

myst.yml

@@ -0,0 +1,33 @@
+# See docs at: https://mystmd.org/guide/frontmatter
+version: 1
+project:
+  id: 9db2473e-461d-4266-86fa-a2a0ea3eb2c9
+  title: executable-tutorials
+  description: Executable tutorials for Scientific Python
+  keywords: []
+  authors: [Scientific Python Developers]
+  github: https://github.com/scientific-python/executable-tutorials
+  # To autogenerate a Table of Contents, run "myst init --write-toc"
+  toc:
+    # Auto-generated by `myst init --write-toc`
+    - file: index.md
+    - title: Tutorials
+      children:
+        - title: Executable
+          children:
+            - file: tutorials/executable/basics.md
+        - title: Matplotlib
+          children:
+            - file: tutorials/matplotlib/interactive_mpl.md
+            - file: tutorials/matplotlib/static_mpl.md
+        - title: Static
+          children:
+            - file: tutorials/static/static.md
+    - file: contributing.md
+    - file: maintainers.md
+    
+site:
+  template: book-theme
+  # options:
+  #   favicon: favicon.ico
+  #   logo: site_logo.png