Add github workflow to launch Chromium and dump its tree on Linux

[elima]

This will supersede existing workflow because it already include building the NodeJS module on Linux.

The workflow will:

• Install and launch headless chromium
• Build acacia native library, examples and tests; and NodeJS module, example and tests (see AT-SPI Python module fails to build on CI runner #195 to understand why not Python).
• Run the test suite via ctest (make test).
• Dump the chromium a11y tree from native and nodejs dump_tree_atspi examples.

There is a timeout of 5 minutes for the whole workflow. We should remember to increase it if we make it more complex in the future, or if it starts to fail due to timeout.

[elima]

Ok, some more progress:

• Finally I think I fixed the flakiness running dump_tree. At least I have not got any new failure in the last ~15 runs.
• I found a problem with the linked libraries of the NodeJS module. In the github runner (and only in the runner), specifying the atspi library via pkgconfig --libs in bindings.gyp didn't work. I found a solution by specifying the dependency libraries in a new "libraries" section in binding.gyp.in. So that is the somewhat unrelated hunk in this patch about.
• I found that Python binding doesn't build in the github runner. SWIG fails saying it can't find std_unique_ptr.i. Oddly enough, NodeJS module builds ok. I have filed AT-SPI Python module fails to build on CI runner #195 to track this issue. But this means that this workflow has python disabled so the chromium a11y tree is only dumped from native and nodejs dump_tree_atspi examples.

I'm opening this up for review as-is.

[spectranaut]

hurray!