Fix typos discovered by codespell (#1496)

# https://pypi.org/project/codespell
% `codespell`
```
./emsdk.py:1459: thier ==> their
./test/test.bat:1: equivilent ==> equivalent
./test/test.py:198: Specificlly ==> Specifically
./scripts/update_bazel_workspace.py:2: revisons ==> revisions
./scripts/update_node.py:11: direcotry ==> directory
./bazel/emscripten_toolchain/BUILD.bazel:57: implictly ==> implicitly
./docker/Dockerfile:87: terninal ==> terminal
```

test/test.py

@@ -195,7 +195,7 @@ int main() {
     check_call(upstream_emcc + ' hello_world.c')
 
   def test_closure(self):
-    # Specificlly test with `--closure` so we know that node_modules is working
+    # Specifically test with `--closure` so we know that node_modules is working
     check_call(upstream_emcc + ' hello_world.c --closure=1')
 
   def test_specific_version(self):