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

[David Linus Briemann]

Add an .editorconfig to define indentation, trim trailing whitespace and open curly brace position for C++ and Java.
This allows various editors to easily infer basics of the coding style.

-------------

Commit messages:
 - add editorconfig for better indentation detection

Changes: https://git.openjdk.org/jdk/pull/23693/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23693&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311227
  Stats: 17 lines in 1 file changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/23693.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23693/head:pull/23693

PR: https://git.openjdk.org/jdk/pull/23693