add WSL build instructions

Build_on_Windows.md

+# Building Biocham on Windows 10
+
+Biocham may be built on Windows 10 using the Windows Subsystem for Linux.
+
+## Steps
+
+First, install WSL as per the [instructions](https://docs.microsoft.com/en-us/windows/wsl/install-win10), then install the Ubuntu distribution from the Windows store.
+
+
+Run Ubuntu and obtain the Biocham sources (e.g. through git)
+
+
+Then, run `./install.sh` from the source directory to install the project's dependencies and build Biocham.
+
+Follow the instructions given by the install script (e.g. `source ~/.profile` at the end to update the path).
+
+## Running Biocham
+
+As with linux, run `./biocham --notebook` for instance to open a Jupyter notebook that talks to a Biocham kernel.
+
+## Notes
+
+WSL is apparently available on recent releases of Windows Server, but is untested on our side.