fix(v4): add symlink for default README (#584)

.github/README.md

@@ -0,0 +1 @@
+../v4/README.md

v4-migration-guide.md

@@ -26,7 +26,7 @@ theme = "bilberry-hugo-theme/v4"
 ### Syntax Highlighting
 
 No modifications are needed for posts with any existing code blocks. Syntax highlighting will work the same way as with
-the `v3` version. Please see the [Syntax Highlighting](README.md#syntax-highlighting) section in the `v4` **README** 
+the `v3` version. Please see the [Syntax Highlighting](v4/README.md#syntax-highlighting) section in the `v4` **README** 
 guide for customization options.
 
 ### Color and Font Customizations
@@ -35,7 +35,7 @@ In `v3`, color and font customizations were handled directly in the `assets/sass
 the `_variables.scss` file no longer exists and such customization is done in the `config.toml` by defining
 corresponding parameters from the `assets/sass/theme.scss` file, for example, `baseColor`, `headlineFont` etc.
 Therefore, any changes you made in `_variables.scss` file should be ported to your site's configuration file. Read
-the [Colors and Fonts](README.md#colors-and-fonts) section in the `v4` **README** guide for more details.
+the [Colors and Fonts](v4/README.md#colors-and-fonts) section in the `v4` **README** guide for more details.
 
 ### Image Modal Zoom
 

README.md → v4/README.md

@@ -10,7 +10,7 @@
 
 ----
 
-This guide is for `v4` version. For `v3`, please use this [guide](v3-README.md).
+This guide is for `v4` version. For `v3`, please use this [guide](../v3-README.md).
 
 **IMPORTANT** `v3` will be supported until **August 31, 2024**. Only critical bugs will be fixed during this period, no
 new features will be implemented.
@@ -927,7 +927,7 @@ Read Hugo's [documentation](https://gohugo.io/content-management/syntax-highligh
 ### Colors and Fonts
 
 Styling is implemented using SCSS along with [npm](https://www.npmjs.com/), which is only used for dependency management. Colors and fonts can be customized via variables defined in
-the [`assets/sass/theme.scss`](v4/assets/sass/theme.scss) file.
+the [`assets/sass/theme.scss`](assets/sass/theme.scss) file.
 
 For example, if you want to customize the `$base-color` variable, you should define the `baseColor` parameter in your
 site's `config.toml` file.