docs: add block indents values

.storybook/stories/documentation/Blocks.mdx

@@ -17,10 +17,24 @@ Each block has the following common properties:
 `resetPaddings: boolean` — Allows resetting top and bottom margins standard for all blocks. **Deprecated**, use `indent` instead
 
 `indent?: {
-  top?: string
+  top?: string,
   bottom?: string
 }` - block indentation at the top and bottom, default size `l`, examples you can see [here](?path=/story/blocks-cardlayout--with-custom-indents)
 
+**indent size values:**
+
+`0` - 0px
+
+`xs` - 16px
+
+`s` - 24px
+
+`m` - 32px
+
+`l` - 48px
+
+`xl` - 64px
+
 _[Common field types](?id=documentation-types&viewMode=docs)_
 
 ## [Banner](?path=/story/blocks-banner--docs&viewMode=docs)