Blackholio import - README updates (#2947)

Co-authored-by: Zeke Foppa <bfops@users.noreply.github.com>

demo/Blackholio/DEVELOP.md

@@ -0,0 +1 @@
+Please make changes and submit pull requests to the root repository at [SpacetimeDB/demo/Blackholio](https://github.com/clockworklabs/SpacetimeDB/tree/master/demo/Blackholio). The [Blackholio repository](https://github.com/clockworklabs/Blackholio) is only a mirror.

demo/Blackholio/README.md

@@ -33,8 +33,8 @@ If you just want to checkout the final project and play around a bit, follow the
 2. Start SpacetimeDB in a separate terminal with `spacetime start`.
 3. Clone this repository:
    ```bash
-   git clone https://github.com/ClockworkLabs/Blackholio.git
-   cd Blackholio
+   git clone https://github.com/ClockworkLabs/SpacetimeDB.git
+   cd SpacetimeDB/demo/Blackholio
    ```
 4. Publish the server logic. You can either publish the csharp server or the rust server.
    ```bash

modules/benchmarks/README.md

@@ -9,7 +9,7 @@ This provides the various modules used for benchmarking SpacetimeDB, with the cr
 
 ### [`circles.rs`](src/circles.rs)
 
-Implements a smaller variation of the [Blackholio](https://github.com/clockworklabs/Blackholio) game.
+Implements a smaller variation of the [Blackholio](https://github.com/clockworklabs/SpacetimeDB/tree/master/demo/Blackholio) game.
 
 Circles are spawned and then queried to evaluate `CROSS JOIN` performance.
 
@@ -28,4 +28,4 @@ scenarios.
 
 ## How to Run
 
-For detailed instructions on running the benchmarks, refer to the [benchmarks README](../../crates/bench/README.md).  
+For detailed instructions on running the benchmarks, refer to the [benchmarks README](../../crates/bench/README.md).