Document how to use the sbt plugin

Author: jonas

docs/src/paradox/obtaining-bindgen/index.md

@@ -2,6 +2,7 @@
 
 @@@ index
 
+* [Use the sbt plugin](sbt-plugin.md)
 * [Use Docker Container](docker-container.md)
 * [Build Binary with CMake](cmake.md)
 * [Build Binary with docker-compose](docker-compose.md)
@@ -10,6 +11,8 @@
 
 There are 3 ways to obtain bindgen:
 
+ * @ref:[Use the sbt plugin](sbt-plugin.md)
+
  * @ref:[Use docker container](docker-container.md)
 
  * @ref:[Build binary with CMake](cmake.md)

docs/src/paradox/obtaining-bindgen/sbt-plugin.md

@@ -0,0 +1,61 @@
+# Using the sbt plugin
+
+To add the sbt plugin to your project add the following lines in `project/plugins.sbt`:
+
+@@@ vars
+```sbt
+addSbtPlugin("org.scala-native.bindgen" % "sbt-scala-native-bindgen" % "$project.version$")
+
+resolvers += Resolver.bintrayIvyRepo("scala-native-bindgen", "sbt-plugin")
+resolvers += Resolver.bintrayRepo("scala-native-bindgen", "maven")
+```
+@@@
+
+Next configure the plugin using the settings scoped to either `Compile` or `Test`:
+
+|---------------------------|-------------------|
+|`nativeBindgenHeader`      | The C header file to read.
+|`nativeBindgenPackage`     | Package of the enclosing object. No package by default.
+|`name in nativeBindgen`    | Name of the enclosing object.
+|`nativeBindgenLink`        | Name of library to be linked.
+
+@@@ note
+
+By default the `scala-native-bindgen` executable is downloaded automatically for supported platforms. Set `version in nativeBindgen` (unscoped) to configure the version of the `scala-native-bindgen` to use if you want a version different from the version of the sbt plugin.
+
+In case your platform is not supported, you must compile `scala-native-bindgen` yourself and configure the path to the executable using `nativeBindgenPath`, e.g.:
+
+```sbt
+nativeBindgenPath := file("/path/to/scala-native-bindgen")
+```
+
+@@@
+
+Example settings:
+
+```sbt
+enablePlugins(ScalaNativeBindgenPlugin)
+inConfig(Compile)(
+  Def.settings(
+    nativeBindgenHeader := (resourceDirectory in Compile).value / "header.h",
+    nativeBindgenPackage := Some("org.example.mylib"),
+    nativeBindgenLink := Some("mylib"), // Will pass `-lmylib` to the linker
+    nativeBindgenExclude := Some("__"),
+    name in nativeBindgen := "MyLib"
+  ))
+```
+
+Running `nativeBindgen` will generate a file named `target/scala-2.x/src_managed/main/sbt-scala-native-bindgen//ScalaNativeBindgen.scala` containing something along the following lines:
+
+```scala
+package org.example.mylib
+
+import scala.scalanative._
+import scala.scalanative.native._
+
+@native.link("mylib")
+@native.extern
+object MyLib {
+  // ... left out for brevity ...
+}
+```