docs: More tweaks to text and formatting.

Author: microbit-carlos

README.md

@@ -18,6 +18,8 @@ https://microbit-foundation.github.io/microbit-universal-hex/.
 
 ## Web Tool
 
+<img width="30%" alt="microbit-universal-hex logo" src="docs/img/web-tool-screenshot.png" align="left">
+
 An implementation example can be found in the
 [docs/examples/webtool.html](docs/examples/webtool.html) file. This web tool can
 generate a Universal Hex from two Intel Hex files.

docs/api-docs.md

@@ -12,3 +12,5 @@ can be found here:
 
 The source code is well annotated with docstring and
 [TypeDoc](http://typedoc.org) is used to generate the API pages.
+
+![Screenshot of an API page](img/api-screenshot.png)

docs/img/api-screenshot.png

@@ -19,7 +19,9 @@ Create Universal Hex files for the micro:bit.
 [API](api/){: .btn .btn-purple .mb-4 .mb-md-0 .mr-2 }
 [View it on GitHub](https://github.com/microbit-foundation/microbit-universal-hex/){: .btn .mb-4 .mb-md-0 }
 
-<br><hr>
+<br>
+
+---
 
 This is the documentation for the micro:bit Universal Hex library.
 
@@ -34,6 +36,6 @@ micro:bit Universal Hex from two or more micro:bit Intel Hex files.
 
 ## Navigation
 
-- ⬅️ The menu on the left shows you the available documentation pages.
-- ⬆️ The header at the top contains search bar
+- ⬆️ The header at the top contains a search bar
+- ⬅️ The menu on the left shows you the available documentation pages
 - ⬇️ If you'd like to contribute to the docs there is an edit link at the footer