Add experimental build from source instructions

Author: CrazyPython

README.md

@@ -6,6 +6,39 @@ Tree query is a tool that searches across indented lines.
 
 It is a replacement for Roam's query system. It supports everything Roam does, except for block references.
 
+## Installation
+
+### Build from source
+Currently the only supported method. DYI style.
+
+On FreeBSD, GNU+Linux, and macOS, open Terminal and go:
+```
+curl https://dlang.org/install.sh | bash -s
+```
+
+On Windows, download and install [Git Bash](https://gitforwindows.org/):
+```
+mkdir %USERPROFILE%\dlang
+powershell.exe -Command "wget https://dlang.org/install.sh -OutFile %USERPROFILE%\dlang\install.sh"
+```
+
+Then:
+
+```
+~/dlang/install.sh install ldc-1.23.0,dub
+```
+
+Then `cd` into the directory where you cloned this directory and type:
+```
+make tree-query-build
+```
+
+Install to make available eveywhere:
+```
+chmod 700 ~/Downloads/tree-query
+sudo mv ~/Downloads/tree-query /usr/local/bin
+```
+
 ## Quickstart
 
 **Query in current directory:**