Mark TODOs in content

```{admonition} TODO
:class: warning

Add content for this section
```

Author: ksuess

docs/classic-ui/icons.md

@@ -67,7 +67,9 @@ For example the copy icon is named `plone.icon.plone-copy`.
 
 ## Customization
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 Add content for this section
 ```
 
@@ -79,7 +81,9 @@ Add content for this section
 
 ## Icon font
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 Add content for this section
 ```
 
@@ -91,7 +95,9 @@ Add content for this section
 
 ## Iconresolver
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 What is `iconresolver`?
 Add to Glossary.
 ```

docs/classic-ui/index.md

@@ -10,7 +10,9 @@ html_meta:
 
 # Classic UI
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 Perhaps some of this introduction should be an include, so we don't have to repeat ourselves?
 ```
 

docs/classic-ui/theming/barceloneta.md

@@ -10,7 +10,9 @@ html_meta:
 
 # Plone Classic UI Theming Based on Barceloneta
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 This page is only an outline and needs a lot of work.
 ```
 

docs/classic-ui/theming/from-scratch.md

@@ -10,7 +10,9 @@ html_meta:
 
 # Plone Classic UI Theming based on Barceloneta
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 This page is only an outline and needs a lot of work.
 ```
 

docs/classic-ui/theming/index.md

@@ -10,7 +10,9 @@ html_meta:
 
 # Plone 6 Classic UI Theming
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 This page is only an outline and needs a lot of work.
 ```
 

docs/classic-ui/theming/through-the-web.md

@@ -10,7 +10,9 @@ html_meta:
 
 # Through-the-web (TTW) Theme Customization in Plone 6 Classic UI
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 This page is only an outline and needs a lot of work.
 ```
 
@@ -34,7 +36,9 @@ It is shipped as the last resource after all other CSS files.
 It can be used to override default CSS, sometimes with the use of the CSS property `!important` or specific CSS selectors.
 
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 Provide usage.
 Provide navigation through {menuselection}`Site Setup --> Theming` or {guilabel}`Button Name`.
 Add screenshots.
@@ -48,7 +52,9 @@ Add screenshots.
 Plone uses Twitter Bootstrap's CSS variables.
 They are used to tweak colors, fonts, spacing, and other CSS attributes.
 
-```{todo}
+```{admonition} TODO
+:class: warning
+
 Provide usage.
 ```