Add mechanisms with electron cross section data (Cantera/cantera#1887)

README.md

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+# Cantera Example Data Files
+
+This repository provides data files used by various Cantera examples, which can be seen
+at https://cantera.org/stable/examples/python/index.html. In particular, many of the
+input files found here are based on scientific publications and are meant to demonstrate
+Cantera's capabilities with more realistic and interesting reaction systems than those
+based only on the basic mechanisms provided in the main Cantera repository.
+
+## Adding files for new examples
+
+To implement an example requiring a new input file, the following steps should be
+followed:
+
+- Create your new example in your local Git checkout of Cantera.
+- Create the new input file in the `data/example_data` subdirectory.
+- Commit the example to a new feature branch.
+  * :warning: Make sure you _do not_ add the input file or an update of the
+    `example_data` submodule to this branch.
+- Commit the input file to a feature branch in the `example_data` submodule.
+- Create a pull request for your example in the main Cantera repository
+- Create a pull request in the `cantera-example-data` repository which includes the text
+  `(Cantera/cantera#XYZ)` where `XYZ` is the number of your PR in the main repository.
+  * The CI process in the main repository will automatically check out this submodule
+    PR so the new input file is available for those jobs that run the examples.
+  * You should see one failing job, with the description `Linters / Check for unmerged
+    example-data pull request (pull_request)`. This is a reminder for maintainers for
+    the remaining steps that need to be completed before merging the PR.
+- Once PR reviews are completed and all expected tests pass, the PR on the
+  `cantera-example-data` can be merged.
+- Finally, the PR branch for the main repository can be updated to include the update
+  of the `example_data` submodule, and this PR can be merged.
+