Add ClusterFuzzLite set up

[DavidKorczynski]

Description

Add continuous fuzzing set up by way of ClusterFuzzLite. This will run the attached fuzzer for each PR such 180 seconds and if any issues are found these will be flagged.

Test Steps

To reproduce this by way of OSS-Fuzz (which ClusterFuzzLite will be using):

git clone https://github.com/google/oss-fuzz
git clone https://github.com/DavidKorczynski/coreJSON corejson
cd corejson
git checkout clusterfuzz-initial

# Build the fuzzers in .clusterfuzzlite
python3 ../oss-fuzz/infra/helper.py build_fuzzers --external $PWD

# Run the fuzzer for 10 seconds
python3 ../oss-fuzz/infra/helper.py run_fuzzer --external $PWD validate_fuzzer -- -max_total_time=10

Checklist:

• I have tested my changes. No regression in existing tests.
• I have modified and/or added unit-tests to cover the code changes in this Pull Request.

This is adding essentially another test and not a feature.

Related Issue

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[ActoryOu]

Really appreciate this change. Approve in advance.
One minor comment is - could you help to add the test steps in readme file to help people reproduce?

[DavidKorczynski]

One minor comment is - could you help to add the test steps in readme file to help people reproduce?

Yes, done!