Fix instructions

* Update `subtitle` documentation to note that HTML escape sequences are
restricted by the new Goldmark rendering engine
* Add documentation for the `mainSections` parameter

README.md

@@ -13,7 +13,7 @@ instructions on how to install Hugo, create a site, and install a theme.
 Installing the theme as a git submodule is the preferred way.
 
 ```
-git add submodule https://git.thecorams.net/kevin/basic-theme.git themes/basic-theme
+git submodule add https://git.thecorams.net/kevin/basic-theme.git themes/basic-theme
 ```
 
 ### Example Site
@@ -35,16 +35,34 @@ As a very basic theme, there is very little to be configured via the `config.tom
 file.
 
 The footer layout file uses Hugo's `markdownify` pipe to display the `copyright` 
-configuration setting, providing support both for HTML5 character escape
+configuration setting, providing support both for HTML character escape
 sequences such as `©` as well as markdwn formatting and links.
 
-The only non-standard configuration setting is the `subtitle` parameter:
+Note: Hugo versions 0.60.0 and up will have restrictions on using embedded HTML, 
+including escape secquences, unless the Goldmark renderer is configure with
+`unsafe = true`.
+
+### `subtitle` parameter
+
+Setting the `subtitle` parameter adds a secondary header underneath the `title`
+in the site header.
 
 ```toml
 [params]
   subtitle = "A sub-title for your site"
 ```
 
+### `mainSections` parameter
+
+Setting the `mainSections` parameter restricts the pages that appear on the
+homepage.
+
+```toml
+[params]
+  mainSections = ["posts"]
+
+```
+
 ## Theme Organization
 
 ### Semantic Content Organization
@@ -145,6 +163,12 @@ organization. The [list](layouts/_default/list.html) and
 [single](layouts/_default/single.html) templates display the page title as 
 a `<h1>...</h1>` level header.
 
+#### content-menu
+
+This block is for providing navigation menu(s) for the main content, matching
+with the `<nav>...</nav>` block inside the main header. The block is currently
+a place holder, with no default implementation.
+
 #### content
 
 This block is for the content of the page.