Improve MDX alert block spacing from following paragraph text (#703)

* Initial plan

* fix: add bottom spacing after mdx alerts

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Co-authored-by: lilin90 <30922556+lilin90@users.noreply.github.com>

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: lilin90 <30922556+lilin90@users.noreply.github.com>

Author: Copilot

src/components/MDXComponents/Alert.tsx

@@ -11,6 +11,7 @@ function AlertContainer(props: { children: React.ReactNode }) {
     <Box
       sx={{
         paddingTop: "1rem",
+        marginBottom: "1rem",
         "& .MuiAlert-message p": {
           marginBottom: 0,
           marginTop: 0,