PARQUET-2426: Add lz4_raw compression to README

[cxzl25]

Make sure you have checked all steps below.

Jira

• My PR addresses the following Parquet Jira issues and references
  them in the PR title. For example, "PARQUET-1234: My Parquet PR"
  • https://issues.apache.org/jira/browse/PARQUET-2426
  • In case you are adding a dependency, check if the license complies with
    the ASF 3rd Party License Policy.

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines. In addition, my commits follow the guidelines
  from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Style

• My contribution adheres to the code style guidelines and Spotless passes.
  • To apply the necessary changes, run mvn spotless:apply -Pvector-plugins

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain Javadoc that explain what it does

[cxzl25]

Thanks @wgtmac fix CI and comments!