Be more explicit about Git LFS workflow

README.md

@@ -15,8 +15,12 @@ a high CPU and RAM load when opening the project for the first time.
 
 This demo uses [Git LFS](https://git-lfs.github.com/) to store the heaviest assets.
 
-You need to install Git LFS on your system, and then fetch the assets from the LFS
-repository with:
+You need to install the Git LFS extension on your system, so that Git can fetch the
+assets from the LFS repository. It should happen automatically when using the usual
+Git commands.
+
+If you cloned this Git repository *before* installing Git LFS, you will have to fetch
+the assets manually the first time:
 
 ```text
 git lfs fetch

screenshot.png.import

@@ -0,0 +1,31 @@
+[remap]
+
+importer="texture"
+type="StreamTexture"
+path="res://.import/screenshot.png-024a21af5d37bf0f0dd0e2bccdd149d0.stex"
+
+[deps]
+
+source_file="res://screenshot.png"
+dest_files=[ "res://.import/screenshot.png-024a21af5d37bf0f0dd0e2bccdd149d0.stex" ]
+
+[params]
+
+compress/mode=0
+compress/lossy_quality=0.7
+compress/hdr_mode=0
+compress/bptc_ldr=0
+compress/normal_map=0
+flags/repeat=0
+flags/filter=true
+flags/mipmaps=false
+flags/anisotropic=false
+flags/srgb=2
+process/fix_alpha_border=true
+process/premult_alpha=false
+process/HDR_as_SRGB=false
+process/invert_color=false
+stream=false
+size_limit=0
+detect_3d=true
+svg/scale=1.0