📚 Docs for exclude during project toc generation

docs/table-of-contents.md

@@ -57,6 +57,25 @@ The “root” of a site is the page displayed when someone browses to the index
 All of these can be over-ridden by choosing an explicit `_toc.yml`, when that is present it will be used.
 ```
 
+### Excluding Files
+
+If there are markdown or notebook files within a project folder that you do not want included in your project, you may list these in the `myst.yml` project frontmatter under `exclude`. For example, to ignore a single file `notes.md`, all notebooks in the folder `hpc/`, and all files named `ignore.md`:
+
+```yaml
+project:
+  exclude:
+    - notes.md
+    - hpc/*.ipynb
+    - '**/ignore.md'
+```
+
+Additionally, files excluded in this way will also not be watched during `myst start`. This may be useful if you have a folder with a huge number of files (many thousands?) that causes `myst start` to crash. For example, in the `data/` directory, there may be no markdown and no notebooks but 100,000 small data files:
+
+```yaml
+project:
+  exclude: data/**
+```
+
 (toc-format)=
 
 ## Defining a `_toc.yml` using Jupyter Book’s format