Add presentation that shows how to add a logo

exampleSite/content/logo-example/_index.md

@@ -0,0 +1,99 @@
++++
+title = "Logo presentation example"
+outputs = ["Reveal"]
+[logo]
+src = "/images/github-logo.png"
+alt = "GitHub logo with Octocat"
+[reveal_hugo]
+custom_theme = "reveal-hugo/themes/robot-lung.css"
+margin = 0.2
++++
+
+## logo-example
+
+This presentation shows how to add a logo to each slide, like the GitHub one you see above.
+
+You can generalize the concept to add any additional markup to your presentations.
+
+---
+
+First, create a partial called `body.html` and put it in this directory:
+
+```text
+layouts/partials/{section}/reveal-hugo/body.html
+```
+
+---
+
+Substitute `{section}` for `home` if you are adding a logo to the presentation at `content/_index.md`. Otherwise, substitute the name of the Hugo section where your presentation lives. 
+
+---
+
+The presentation you're looking at right now is in `content/logo-example`, so the partial to add the logo lives in:
+
+```text
+layouts/partials/logo-example/reveal-hugo/body.html
+```
+
+---
+
+💡 Tip: to make the logo appear in every presentation, put it here:
+
+```text
+layouts/partials/reveal-hugo/body.html
+```
+
+---
+
+💡 Tip: In addition to `body.html`, you can create partials `head.html` and `end.html` in any of those directories. 
+
+---
+
+- head.html: Add markup just before the closing `</head>` tag
+- body.html: Add markup just before the closing `</body>` tag
+- end.html: Add markup just before the closing of the Reveal.js `div.slides` container
+
+---
+
+Once the partial exists in `body.html`, we can add our image tag to it:
+
+```html
+<img id="logo" src="{{ .Param "logo.src" }}" alt="{{ .Param "logo.alt" }}">
+```
+
+---
+
+In this example, the src and alt attributes are set to values from the content's front matter or site's configuration, which you can see in `logo-example/_index.md`:
+
+```toml
+[logo]
+src = "/images/github-logo.png"
+alt = "GitHub logo with Octocat"
+```
+
+---
+
+To position the logo, we can add a style tag to `body.html`:
+
+```html
+<style>
+  #logo {
+    position: absolute;
+    top: 20px;
+    left: 20px;
+    width: 250px;
+  }
+</style>
+```
+
+<small>
+💡 Depending on the theme you're using, your styles will be different. <br>You may also prefer to put your CSS in an external file or your Reveal.js theme.
+</small>
+
+---
+
+# 🤗
+
+That's it.
+
+Happy Hugo-ing!