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
```

emsdk.py

@@ -1456,7 +1456,7 @@ def get_required_path(active_tools):
       # the tools path to the users path if a program by that name is found
       # in the existing PATH.  This allows us to, for example, add our version
       # node to the users PATH if, and only if, they don't already have a
-      # another version of node in thier PATH.
+      # another version of node in their PATH.
       if hasattr(tool, 'activated_path_skip'):
         current_path = which(tool.activated_path_skip)
         # We found an executable by this name in the current PATH, but we