Update changelog for add_poyline
- DEPRECATED: `InputFloat` and `InputInt` have been deprecated. `ui.input_float` and `ui.input_int` are _not_, however, and instead will just call `input_scalar` as appropriate. Therefore, please switch your code to `ui.input_float` or `ui.input_int`.
+- Added `add_polyline` method to `DrawListMut`, which binds to Dear ImGui's `AddPolyline` and `AddConvexPolyFilled`
+
## [0.8.0] - 2021-09-17
Welcome to the `0.8.0` update. This is one of the largest updates imgui-rs has ever seen; it will generate errors in a `0.7` project, but hopefully it should be both quick to fix, and enjoyable to update. See our [release page](https://github.com/imgui-rs/imgui-rs/releases/tag/v0.8.0) for more information and a list of contributors to this cycle. Thank you to everyone who uses `imgui-rs`, files issues, and spend their time and effort to PR new changes into the codebase. Because of all that effort, this is by far the best `imgui-rs` has looked!
