DevTools: Improve jsconfig.json accuracy
DevTools: Improve jsconfig.json accuracy

This adds some excludes (from our eslintignore) and extra
compilerOptions (from TypeScript's tsconfig.json for devtools-frontend)
that should make VSCode intellisense faster and more accurate for
DevTools.

Change-Id: I514e29ab7e9b9f9395ecdc672aadc5a8c01c3564
Reviewed-on: https://chromium-review.googlesource.com/1030852
Commit-Queue: Joel Einbinder <bab755abe9fee48fe544272e55f73517d4e4a725@chromium.org>
Reviewed-by: Dmitry Gozman <0ca14b32cbb359a30ac562af27dd84cc2813eacb@chromium.org>
Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#554149}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 24216a91229cf550149b107508b7a1354a4fcb38
ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend,dart-archive/devtools-frontend,ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend,dart-archive/devtools-frontend,dart-archive/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,ChromeDevTools/devtools-frontend,dart-archive/devtools-frontend