RFR: 8311227: Add .editorconfig so IDEs would pick up the common settings automatically: indent, trim trailing whitespace

[Magnus Ihse Bursie]

Alternative to https://github.com/openjdk/jdk/pull/23693 for implementing JDK-8311227.

This `.editorconfig` file is a 1-to-1 conversion of the checks done by jcheck into .editorconfig format. I believe that is a better way to introduce an `.editorconfig` file into the existing JDK project.

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Commit messages:
 - 8311227: Add .editorconfig

Changes: https://git.openjdk.org/jdk/pull/24448/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24448&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311227
  Stats: 7 lines in 1 file changed: 7 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24448.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24448/head:pull/24448

PR: https://git.openjdk.org/jdk/pull/24448