[gnome-builder] doc: Add instructions for Rust language server

[Christian Hergert <chergert src gnome org>]

commit ee57e51300f8bd82c5ebdeed37a0892476484fec
Author: Tobias Schönberg <tobias47n9e gmail com>
Date:   Tue Oct 31 21:56:23 2017 +0100

    doc: Add instructions for Rust language server
    
    https://bugzilla.gnome.org/show_bug.cgi?id=789737

 doc/howto/index.rst            |    2 +-
 doc/howto/rust_integration.rst |   20 ++++++++++++++++++++
 2 files changed, 21 insertions(+), 1 deletions(-)
---
diff --git a/doc/howto/index.rst b/doc/howto/index.rst
index af8f0c7..4a7ebe5 100644
--- a/doc/howto/index.rst
+++ b/doc/howto/index.rst
@@ -16,4 +16,4 @@ Contents
    search_and_replace
    jump_to_definition
    search_for_symbol
-
+   rust_integration
diff --git a/doc/howto/rust_integration.rst b/doc/howto/rust_integration.rst
new file mode 100644
index 0000000..037a498
--- /dev/null
+++ b/doc/howto/rust_integration.rst
@@ -0,0 +1,20 @@
+################
+Rust integration
+################
+
+First install `rustup`. Use the installer in `Preferencees->SDKs` or the instructions at rustup_.
+This will install all the components into `~/.cargo`.
+Then go to `Preferencees->SDKs->Rustup Toolchains` and press `+` to add a new Rust channel and use `nightly` 
as the name.
+
+After that, open a terminal and install the Rust language-server:
+
+.. code-block:: bash
+
+    $ ~/.cargo/bin/rustup component add rls-preview --toolchain nightly
+    $ ~/.cargo/bin/rustup component add rust-analysis --toolchain nightly
+    $ ~/.cargo/bin/rustup component add rust-src --toolchain nightly
+
+These instructions are taken from the rls-repo_, where you can check for up-to-date instructions.
+
+.. _rustup: https://www.rustup.rs/
+.. _rls-repo: https://github.com/rust-lang-nursery/rls