docs: improve contributing docs for code snippets (#2546)

* docs: improve contributing docs for code snippets

* chore: use placeholder

docs/contributing_docs.md

@@ -3,10 +3,25 @@
 The _Testcontainers for Go_ documentation is a static site built with [MkDocs](https://www.mkdocs.org/).
 We use the [Material for MkDocs](https://squidfunk.github.io/mkdocs-material/) theme, which offers a number of useful extensions to MkDocs.
 
-In addition we use a [custom plugin](https://github.com/rnorth/mkdocs-codeinclude-plugin) for inclusion of code snippets.
-
 We publish our documentation using Netlify.
 
+## Adding code snippets
+
+To include code snippets in the documentation, we use the [codeinclude plugin](https://github.com/rnorth/mkdocs-codeinclude-plugin), which uses the following syntax:
+
+&lt;!--codeinclude--&gt;<br/>
+&#91;Human readable title for snippet&#93;(./relative_path_to_example_code.go) targeting_expression<br/>
+&#91;Human readable title for snippet&#93;(./relative_path_to_example_code.go) targeting_expression<br/>
+&lt;!--/codeinclude--&gt;<br/>
+
+Where each title snippet in the same `codeinclude` block would represent a new tab
+in the snippet, and each `targeting_expression` would be:
+
+- `block:someString` or
+- `inside_block:someString`
+
+Please refer to the [codeinclude plugin documentation](https://github.com/rnorth/mkdocs-codeinclude-plugin) for more information.
+
 ## Previewing rendered content
 
 ### Using Python locally