Fix markdown formatting for hongdown

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dodok8

docs/manual/integration.md

@@ -872,7 +872,7 @@ instead of `astro`:
 ~~~~
 
 
-SolidStart
+Solidstart
 ----------
 
 *This API is available since Fedify 2.1.0.*

packages/solidstart/README.md

@@ -1,6 +1,6 @@
 <!-- deno-fmt-ignore-file -->
 
-@fedify/solidstart: Integrate Fedify with SolidStart
+@fedify/solidstart: Integrate Fedify with solidstart
 ====================================================
 
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