Add .flake8 to allow for python style checking.

All the whitespace checks need to be disabled because we use 2-space
indentation.

One day this could become part of a presubmit but for now its useful
simply to be able to run the flake8 tools directly on a file in the v8
repo.

Change-Id: I9d7ede102aaa17a7c6e7bf29887565ea2deeb887
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1697055Reviewed-by: Adam Klein <adamk@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Sam Clegg <sbc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62835}

.flake8

+[flake8]
+ignore = E111,E114,E310 # We use 2-space indentation
+exclude =
+ ./third_party/, # third-party code
+ ./build/, # third-party code
+ ./buildtools/, # third-party code
+ ./tools/swarming_client/, # third-party code
+ ./test/wasm-js/, # third-party code
+ ./test/wasm-js/data/, # third-party code
+ ./test/test262/data/, # third-party code
+ ./test/test262/harness/, # third-party code

OWNERS

@@ -5,6 +5,7 @@ file://ENG_REVIEW_OWNERS
 per-file .clang-format=file://INFRA_OWNERS
 per-file .clang-tidy=file://INFRA_OWNERS
 per-file .editorconfig=file://INFRA_OWNERS
+per-file .flake8=file://INFRA_OWNERS
 per-file .git-blame-ignore-revs=file://INFRA_OWNERS
 per-file .gitattributes=file://INFRA_OWNERS
 per-file .gitignore=file://INFRA_OWNERS