Add ns-viewer command to run viewer only with model in eval mode (#1379)

* Add ns-viewer command to run only viewer with model in eval mode

* Remove profiler and logger

* Fix ns-viewer

* ns-viewer remove writer.setup_local_writer

* ns-viewer add writer.setup_local_writer

* ns-viewer: update docs

* Delete outputs

docs/quickstart/first_nerf.md

@@ -30,7 +30,7 @@ Navigating to the link at the end of the terminal will load the webviewer. If yo
 - All data configurations must go at the end. In this case, `nerfstudio-data` and all of its corresponding configurations come at the end after the model and viewer specification.
   :::
 
-## Resume from checkpoint / visualize existing run
+## Resume from checkpoint
 
 It is possible to load a pretrained model by running
 
@@ -40,6 +40,14 @@ ns-train nerfacto --data data/nerfstudio/poster --load-dir {outputs/.../nerfstud
 
 This will automatically start training. If you do not want it to train, add `--viewer.start-train False` to your training command.
 
+## Visualize existing run
+
+Given a pretrained model checkpoint, you can start the viewer by running
+
+```bash
+ns-viewer --load-config {outputs/.../config.yml}
+```
+
 ## Exporting Results
 
 Once you have a NeRF model you can either render out a video or export a point cloud.