[gtk-web/new-website] Fill out the "dev tools" section

[Emmanuele Bassi <ebassi src gnome org>]

commit 1b483a5d2b137bb22a0e11d7ae5760a7cff7df4c
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Feb 18 19:02:19 2020 +0000

    Fill out the "dev tools" section
    
    Use the "how to build a GTK application" section of the API reference.

 collections/_docs/dev-tools.md | 57 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 56 insertions(+), 1 deletion(-)
---
diff --git a/collections/_docs/dev-tools.md b/collections/_docs/dev-tools.md
index cd81635..21cec3a 100644
--- a/collections/_docs/dev-tools.md
+++ b/collections/_docs/dev-tools.md
@@ -1,4 +1,59 @@
 ---
 permalink: /docs/:name/
 ---
-tools
\ No newline at end of file
+
+# Using GTK
+
+To compile a GTK application, you need to tell the compiler where to find
+the GTK header files and libraries. This is done with the
+[`pkg-config`](https://www.freedesktop.org/wiki/Software/pkg-config/)
+utility.
+
+The following interactive shell session demonstrates how `pkg-config` is used
+(the actual output on your system may be different):
+
+```sh
+$ pkg-config --cflags gtk+-3.0
+ -pthread -I/usr/include/gtk-3.0 
+ -I/usr/lib64/gtk-3.0/include
+ -I/usr/include/atk-1.0
+ -I/usr/include/cairo
+ -I/usr/include/pango-1.0
+ -I/usr/include/glib-2.0
+ -I/usr/lib64/glib-2.0/include
+ -I/usr/include/pixman-1
+ -I/usr/include/freetype2
+ -I/usr/include/libpng12
+$ pkg-config --libs gtk+-3.0
+ -pthread
+ -lgtk-3
+ -lgdk-3
+ -latk-1.0
+ -lgio-2.0
+ -lpangoft2-1.0
+ -lgdk_pixbuf-2.0
+ -lpangocairo-1.0
+ -lcairo
+ -lpango-1.0
+ -lfreetype
+ -lfontconfig
+ -lgobject-2.0
+ -lgmodule-2.0
+ -lgthread-2.0
+ -lrt
+ -lglib-2.0
+```
+
+The simplest way to compile a program is to use the "backticks" feature of
+the shell. If you enclose a command in backticks (not single quotes), then
+its output will be substituted into the command line before execution. So to
+compile a GTK "Hello, World" application, you would type the following:
+
+```sh
+$ cc `pkg-config --cflags gtk+-3.0` hello.c -o hello `pkg-config --libs gtk+-3.0`
+```
+
+# Development environments
+
+You can use various integrated development environments to write your GTK
+applications, as well as contributing to GTK.