How to upgrade TypeScript.

The files in this directory are mostly from the TypeScript repository. We currently (unfortunately) have a rather manual process for upgrading TypeScript. It works like this currently:

1. Checkout denoland/TypeScript repo in a separate directory.
2. Add Microsoft/TypeScript as a remote and fetch its latest tags
3. Checkout a new branch based on this tag.
4. Cherry pick the custom commit we made in a previous release to the new one.
5. This commit has a "deno.ts" file in it. Read the instructions in it.
6. Copy typescript.js into Deno repo.
7. Copy d.ts files into dts directory.

So that might look something like this:

git clone https://github.com/denoland/TypeScript.git
cd typescript
git remote add upstream https://github.com/Microsoft/TypeScript
git fetch upstream
git checkout v3.9.7
git checkout -b branch_v3.9.7
git cherry pick <previous-release-branch-commit-we-did>
npm install
gulp local
rsync lib/typescript.js ~/src/deno/cli/tsc/00_typescript.js
rsync --exclude=protocol.d.ts --exclude=tsserverlibrary.d.ts --exclude=typescriptServices.d.ts lib/*.d.ts ~/src/deno/cli/dts/