Add doc of using overrides with pre-commit

Document using included dictionaries on files for which they are not normally used
(for example, Bash words on Markdown or text files), when using `pre-commit`.

Signed-off-by: Daniel F. Dickinson <dfdpublic@wildtechgarden.ca>

Author: danielfdickinson

README.md

@@ -13,7 +13,16 @@ repos:
       - id: cspell
 ```
 
-## Setup Custom Dictionary
+## Using additional dictionaries
+
+### Using included dictionaries on non-standard files
+
+For example, using Bash dictionary with Markdown or text files, by filename (the
+default is to only apply from within VSCode for files of type `shellscript`).
+
+[Using CSpell overrides](docs/README-OVERRIDES.md)
+
+### Setup Custom Dictionary
 
 To use a custom dictionary with the `pre-commit` hook, create either a `cspell.config.yaml` or `cspell.json` file in your project's root directory.
 

docs/README-OVERRIDES.md

@@ -0,0 +1,78 @@
+# Using CSpell overrides
+
+This is the same for use with `pre-commit` as with other methods of invoking
+`cspell`, namely configuring an `overrides` section on your `cspell.json`
+or equivalent file.
+
+The [current overrides documentation on the
+website](https://cspell.org/configuration/overrides/) is rather sparse, so here
+is another example.
+
+## Using Bash dictionary with Markdown or text files by filename
+
+Given a `cspell.json` as follows:
+
+``` json
+{
+  "language": "en",
+  "overrides": [
+      {
+          "dictionaries": [
+              "bash"
+          ],
+          "filename": "**/{*.md,*.txt}"
+      }
+  ],
+  "version": "0.2"
+}
+```
+
+And the following, as `test1.md` and as `test1.err`:
+
+``` markdown
+## Sample code block
+
+    if grep -r "something" .; then
+        echo "Found"
+    fi
+
+    case "a string with 3" in
+    with)
+        echo "Why?"
+        ;;
+    esac
+
+    . ./.bash_aliases
+
+    # We should use getopts
+
+    shopt -p
+
+## And another topic
+
+Words, many words.
+```
+
+When `cspell` is invoked `test1.md` should not show errors, but `test1.err`
+should.
+
+## Invoking CSpell
+
+### `pre-commit`
+
+Use a config such as the one in the [README.md](../README.md), stage all files
+(e.g. `git add --all .`), and execute:
+
+``` bash
+pre-commit run --all-files
+```
+
+or commit the changes
+
+``` bash
+git commit
+```
+
+### Command line
+
+`cspell ./test1.*`