Several doc tweaks, based on feedback

docs/guide/extending-default-theme.md

@@ -20,7 +20,7 @@ Before proceeding, make sure to first read [Using a Custom Theme](./custom-theme
 
 ## Customizing CSS
 
-To apply custom CSS, you first need to create a custom VitePress theme. Place the following code into `.vitepress/theme/index.js` which imports the default theme and adds an additional CSS file to the bundle:
+To apply custom CSS, you first need to create a custom VitePress theme. Place the following code into `.vitepress/theme/index.js` (or `.ts` if you prefer TypeScript). This imports the default theme and adds an additional CSS file to the bundle:
 
 ::: code-group
 ```js [.vitepress/theme/index.js]
@@ -77,7 +77,7 @@ Just remember to choose colors that work well in both dark and light modes, unle
 
 If you'd like to use SASS, LESS, or Stylus within your theme, first make sure the relevant pre-processor is installed by running the applicable command:
 
-```bash
+```sh
 # .scss and .sass
 npm install -D sass
 

docs/guide/using-vue.md

@@ -202,7 +202,7 @@ Note that this might prevent certain tokens from being syntax highlighted proper
 
 VitePress has [built-in support](https://vitejs.dev/guide/features.html#css-pre-processors) for CSS pre-processors: `.scss`, `.sass`, `.less`, `.styl` and `.stylus` files. Simply install the pre-processor itself using the applicable command:
 
-```bash
+```sh
 # .scss and .sass
 npm install -D sass
 

docs/reference/default-theme-config.md

@@ -187,7 +187,7 @@ export type SidebarItem = {
 This is typically used to show the "On this page" section, containing links to major headings within the current page.
 
 Setting this value to `false` prevents rendering of aside container.\
-Setting this value to `true` (the default) renders the aside to the right.\
+Setting this value to `true` renders the aside to the right.\
 Setting this value to `left` renders the aside to the left.
 
 If you want to disable it for all viewports, you should use `outline: false` instead.