Add tool-cache (#12)

* Add tool-cache

* Format

* Fix linux bug

* Update readme

* Package zip/unzip

* Reorganize

* Format

* unzip somehow got corrupted, fixing

* Resolve remaining todos

* Don't log everything

* Pass error codes

* linting

* Branding and nits

* Fix for mac

* clean up windows/nix logic

* Clean up tests

* Export HTTPError

* Add option for custom 7z tool

* Lint/format

* Dont wipe temp/tool directories

packages/tool-cache/README.md

@@ -0,0 +1,7 @@
+# `@actions/tool-cache`
+
+> Functions necessary for downloading and caching tools.
+
+## Usage
+
+See [src/tool-cache.ts](src/tool-cache.ts).