Correct path notation for Windows in documentation (#2171)

Fixed an error in the documentation where the incorrect path notation was used for Windows systems. The documentation had paths denoted with "./", which is incorrect for Windows. This has been corrected to ".\", the appropriate notation for Windows.

This change ensures that Windows users correctly follow the instructions in the documentation without encountering any path-related issues.

docs/quickstart/custom_dataset.md

@@ -106,8 +106,8 @@ cd vcpkg
 ```bash
 git clone https://github.com/microsoft/vcpkg
 cd vcpkg
-./bootstrap-vcpkg.bat
-./vcpkg install colmap[cuda]:x64-windows
+.\bootstrap-vcpkg.bat
+.\vcpkg install colmap[cuda]:x64-windows
 ```
 
 :::
@@ -116,8 +116,8 @@ cd vcpkg
 ```bash
 git clone https://github.com/microsoft/vcpkg
 cd vcpkg
-./bootstrap-vcpkg.sh
-./vcpkg install colmap:x64-windows
+.\bootstrap-vcpkg.sh
+.\vcpkg install colmap:x64-windows
 ```
 
 :::