Make libp2p compile for wasm32-unkown-unknown (#2412)

* Make libp2p compile for wasm32-unkown-unknown

* Fix tests

* Add some crates

substrate/.gitlab-ci.yml

@@ -78,6 +78,19 @@ test-linux-stable:                 &test
     - time cargo test --all --release --verbose --locked
     - sccache -s
 
+check-web-wasm:
+  stage:                           test
+  image:                           tomaka/cargo-web:latest
+  allow_failure: true
+  only:
+    - master
+  script:
+    # WASM support is in progress. As more and more crates support WASM, we
+    # should add entries here.
+    - time cargo web build -p substrate-network-libp2p
+    - time cargo web build -p substrate-panic-handler
+    - time cargo web build -p substrate-peerset
+
 .build-only:                      &build-only
   only:
     - master