Add generic types and update tests (#107)

* Add generic types and update tests

* Add generic types to `on`, `off` and `emit` to enable some nicer TS
  usage if you specify what type you're expecting from the `EventData`.
* Move the tests to be TypeScript source. This will help catch errors in
  the tests if there are any type errors.
* Create a new test to test the generic types and make sure they pass
  and error when expected.
* Upgrade to Mocha 8.
* Did some tidying up of the package.json scripts.

* Tweak TS setup to validate tests

* Fix d.ts generation and tests

Co-authored-by: Jason Miller <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/README.md b/README.md
index 0796e5f..b6a8022 100644
--- a/README.md
+++ b/README.md
@@ -110,7 +110,7 @@ const emitter: mitt.Emitter = mitt();
 
 Mitt: Tiny (~200b) functional event emitter / pubsub.
 
-Returns **Mitt**
+Returns **Mitt** 
 
 ### on