Border style (#2292)

* border styles

* docs for border styles

* fix tests

* tests

* tests and docs

* changelog

* implement auto

* style information fix

docs/snippets/border_title_color.md

@@ -0,0 +1,18 @@
+The following examples demonstrates customization of the border color and text style rules.
+
+=== "Output"
+
+    ```{.textual path="docs/examples/styles/border_title_colors.py"}
+    ```
+
+=== "border_title_colors.py"
+
+    ```python
+    --8<-- "docs/examples/styles/border_title_colors.py"
+    ```
+
+=== "border_title_colors.css"
+
+    ```sass
+    --8<-- "docs/examples/styles/border_title_colors.css"
+    ```

docs/snippets/see_also_border.md

@@ -0,0 +1,9 @@
+- [`border-title-align`](./border_title_align.md) to set the title's alignment.
+- [`border-title-color`](./border_subtitle_color.md) to set the title's color.
+- [`border-title-background`](./border_subtitle_background.md) to set the title's background color.
+- [`border-title-style`](./border_subtitle_style.md) to set the title's text style.
+
+- [`border-subtitle-align`](./border_subtitle_align.md) to set the sub-title's alignment.
+- [`border-subtitle-color`](./border_subtitle_color.md) to set the sub-title's color.
+- [`border-subtitle-background`](./border_subtitle_background.md) to set the sub-title's background color.
+- [`border-subtitle-style`](./border_subtitle_style.md) to set the sub-title's text style.