[D1] Footnote syntax fix. Adding missing colon. (#16415)

* Using the caution aside component for 5 GiB limit for D1.
Adding the import limit in the limits table.

* Syntax fix for limits in D1.

src/content/docs/d1/platform/limits.mdx

@@ -41,6 +41,6 @@ Refer to the [Choose a data or storage product](/workers/platform/storage-option
 
 [^2]: A single Worker script can have up to 1 MB of script metadata. A binding is defined as a binding to a resource, such as a D1 database, KV namespace, environmental variable or secret. Each resource binding is approximately 150-bytes, however environmental variables and secrets are controlled by the size of the value you provide. Excluding environmental variables, you can bind up to \~5,000 D1 databases to a single Worker script.
 
-[^3] The imported file is uploaded to R2. See [R2 upload limit](/r2/platform/limits).
+[^3]: The imported file is uploaded to R2. See [R2 upload limit](/r2/platform/limits).
 
 <Render file="limits_increase" product="workers" />