Add README

Summary: Per title.

Reviewed By: danielbuechele

Differential Revision: D17111990

fbshipit-source-id: f5a14b7f0ce544cec324b70b74eeed8d6efb42b0

scripts/stricter/README.md

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+# stricter
+
+A tool for enforcing a strictly decreasing number of TypeScript
+strict mode violations. All this tool does is run `tsc --strict`
+on the current and the previous (Mercurial) revision,
+compares the error count. If there are more errors than before,
+a positive exit code is raised and the regressions printed.
+
+## Usage
+
+Requires [stack](http://haskellstack.org/) to be installed.
+
+```
+./stricter.hs
+```
+
+Bear in mind that this is hard-coded to Mercurial, so you'll
+need to make some changes first if you want to use this in
+git repositories.
+
+## Building
+
+To build the native binaries, run
+
+```
+stack build
+```
+
+The `stricter.lnx64` binary in the parent directory is the result
+of building this on a Linux machine so we can run this more quickly
+in our CI environment.