📚 DOCS: add/update documentation on hiding content and directive

Author: najuzilu

docs/source/syntax.md

@@ -18,6 +18,9 @@ An exercise directive can be included using the `exercise` pattern. The directiv
 * `nonumber` : flag (empty)
 
     Turns off exercise auto numbering.
+* `hidden` : flag (empty)
+
+    Removes the directive from the final output.
 
 **Example**
 
@@ -76,6 +79,9 @@ A solution directive can be included using the `solution` pattern. It takes in t
 * `class` : text
 
     Value of the solution’s class attribute which can be used to add custom CSS or JavaScript.
+* `hidden` : flag (empty)
+
+    Removes the directive from the final output.
 
 ```{note}
 The title of the solution directive links directly to the referred directive.
@@ -184,11 +190,13 @@ static int factorial(int n){
 ````
 
 
-## How to Hide Directives
+## Hide or Remove Directives
+
+### Hide Content
 
-Directives can be hidden using the `dropdown` class which is available through [Sphinx Book Theme](https://sphinx-book-theme.readthedocs.io/en/latest/index.html). For Sphinx projects, add `"sphinx_book_theme"` to your `html_theme` in the `conf.py` to activate the theme in your Sphinx configuration
+The content of directives can be hidden using the `dropdown` class which is available through [Sphinx Book Theme](https://sphinx-book-theme.readthedocs.io/en/latest/index.html). For Sphinx projects, add `"sphinx_book_theme"` to your `html_theme` in the `conf.py` to activate the theme in your Sphinx configuration
 
-```md
+```python
 ...
 html_theme = "sphinx_book_theme"
 ...
@@ -197,7 +205,7 @@ html_theme = "sphinx_book_theme"
 Jupyter Book's default theme is Sphinx Book Theme; therefore, Jupyter Book projects can utilize `dropdown` without having to activate the theme in your Sphinx configuration.
 
 
-To hide the directive, simply add `:class: dropdown` as a directive option.
+To hide the content, simply add `:class: dropdown` as a directive option.
 
 **Example**
 
@@ -231,6 +239,36 @@ for any positive integer $n$.
 ```
 ````
 
+### Remove Directives
+
+Any specific directive can be hidden by introducing the `:hidden:` option. For example, the following example will not be displayed
+
+````md
+```{exercise}
+    :hidden:
+
+    This is a hidden exercise directive.
+```
+````
+
+```{exercise}
+    :hidden:
+
+    This is a hidden exercise directive.
+```
+
+### Remove All Solutions
+
+All solution directives can be removed from the final output by setting `hide_solutions` to `True`. For Sphinx projects, add the configuration key in the `conf.py` file. Jupyter Book projects, should set the configuration key in `_config.yml` as follows
+
+```yaml
+...
+sphinx:
+  config:
+    hide_solutions: True
+...
+```
+
 ## Custom CSS or JavaScript
 
 Custom JavaScript scripts and CSS rules will allow you to add additional functionality or customize how elements are displayed. If you'd like to include custom CSS or JavaScript scripts in Jupyter Book, simply add any files ending in `.css` or `.js` under a `_static` folder. Any files under this folder will be automatically copied into the built book.