Deploying: Maincloud: add section for connecting via SDKs (#311)

* [bfops/maincloud-sdks]: wIP

* [bfops/maincloud-sdks]: WIP

* [bfops/maincloud-sdks]: do thing

* [bfops/maincloud-sdks]: review

---------

Co-authored-by: Zeke Foppa <[email protected]>

Author: bfops

docs/deploying/maincloud.md

@@ -28,3 +28,24 @@ spacetime login
 ---
 
 With SpacetimeDB Maincloud, you benefit from automatic scaling, robust security, and the convenience of not having to manage the hosting environment.
+
+# Connect from Client SDKs
+To connect to your deployed module in your client code, use the host url of `https://maincloud.spacetimedb.com`:
+
+## Rust
+```rust
+DbConnection::builder()
+    .with_uri("https://maincloud.spacetimedb.com")
+```
+
+## C#
+```csharp
+DbConnection.Builder()
+    .WithUri("https://maincloud.spacetimedb.com")
+```
+
+## TypeScript
+```ts
+  DbConnection.builder()
+    .withUri('https://maincloud.spacetimedb.com')
+```