Merge CODEOWNERS Part 1 (#1472)

* Merge CODEOWNERS

* Add the XCM team as owner of /polkadot/xcm

* Update .github/CODEOWNERS

Co-authored-by: Alexander Samusev <41779041+alvicsam@users.noreply.github.com>

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Alexander Samusev <41779041+alvicsam@users.noreply.github.com>

.github/CODEOWNERS

@@ -0,0 +1,75 @@
+# Lists some code owners.
+#
+# A codeowner just oversees some part of the codebase. If an owned file is changed then the
+# corresponding codeowner receives a review request. An approval of the codeowner might be
+# required for merging a PR (depends on repository settings).
+#
+# For details about syntax, see:
+# https://help.github.com/en/articles/about-code-owners
+# But here are some important notes:
+#
+# - Glob syntax is git-like, e.g. `/core` means the core directory in the root, unlike `core`
+#   which can be everywhere.
+# - Multiple owners are supported.
+# - Either handle (e.g, @github_user or @github/team) or email can be used. Keep in mind,
+#   that handles might work better because they are more recognizable on GitHub,
+#   eyou can use them for mentioning unlike an email.
+# - The latest matching rule, if multiple, takes precedence.
+
+# CI
+/.github/ @paritytech/ci @paritytech/release-engineering
+/.gitlab-ci.yml @paritytech/ci
+/.gitlab/ @paritytech/ci
+
+# XCM
+/polkadot/xcm/ @paritytech/xcm
+
+# WASM executor, low-level client <-> WASM interface and other WASM-related code
+/substrate/client/allocator/ @koute
+/substrate/client/executor/ @koute
+/substrate/primitives/panic-handler/ @koute
+/substrate/primitives/runtime-interface/ @koute
+/substrate/primitives/wasm-interface/ @koute
+/substrate/utils/wasm-builder/ @koute
+
+# Systems-related bits and bobs on the client side
+/substrate/client/sysinfo/ @koute
+/substrate/client/tracing/ @koute
+
+# Documentation audit
+/substrate/primitives/runtime @paritytech/docs-audit
+/substrate/primitives/arithmetic @paritytech/docs-audit
+# /primitives/core (to be added later)
+# /primitives/io (to be added later)
+
+# FRAME
+/substrate/frame/ @paritytech/frame-coders @paritytech/docs-audit
+/substrate/frame/nfts/ @jsidorenko @paritytech/docs-audit
+/substrate/frame/state-trie-migration/ @paritytech/frame-coders @cheme
+/substrate/frame/uniques/ @jsidorenko @paritytech/docs-audit
+
+# GRANDPA, BABE, consensus stuff
+/substrate/client/consensus/babe/ @andresilva
+/substrate/client/consensus/grandpa/ @andresilva
+/substrate/client/consensus/pow/ @sorpaas
+/substrate/client/consensus/slots/ @andresilva
+/substrate/frame/babe/ @andresilva
+/substrate/frame/grandpa/ @andresilva
+/substrate/primitives/consensus/pow/ @sorpaas
+
+# BEEFY, MMR
+/substrate/frame/beefy/ @acatangiu
+/substrate/frame/beefy-mmr/ @acatangiu
+/substrate/frame/merkle-mountain-range/ @acatangiu
+/substrate/primitives/merkle-mountain-range/ @acatangiu
+
+# Contracts
+/substrate/frame/contracts/ @athei @paritytech/docs-audit
+
+# NPoS and election
+/substrate/frame/election-provider-multi-phase/ @paritytech/staking-core @paritytech/docs-audit
+/substrate/frame/election-provider-support/ @paritytech/staking-core @paritytech/docs-audit
+/substrate/frame/elections-phragmen/ @paritytech/staking-core @paritytech/docs-audit
+/substrate/frame/nomination-pools/ @paritytech/staking-core @paritytech/docs-audit
+/substrate/frame/staking/ @paritytech/staking-core @paritytech/docs-audit
+/substrate/primitives/npos-elections/ @paritytech/staking-core @paritytech/docs-audit