travis: Add a windows test target.

.travis.yml

@@ -9,6 +9,8 @@ jobs:
   include:
     - stage: Lint
       os: linux
+      before_script:
+        - rustup component add rustfmt
       script:
         - cargo fmt --all -- --check
 
@@ -16,6 +18,8 @@ jobs:
       os: linux
       dist: bionic
 
+    - os: windows
+
     - os: osx
 
     - os: linux
@@ -49,10 +53,6 @@ jobs:
             cd matrix_sdk_base
             cargo test --target wasm32-unknown-unknown --no-default-features
 
-
-before_script:
-  - rustup component add rustfmt
-
 script:
   - cargo build
   - cargo test