build: migrate to typescript (#36)

* build(npm): fix test scripts for windows hosts

* fix(hold): fix most recent event devlivery for late observers

* build: migrate to typescript

* refactor: remove redundant .eslintrc.json

* test: backport recent master changes

* test: postreview

* style: stricter tsconfig

Author: raveclassic

.editorconfig

@@ -0,0 +1,5 @@
+root = true
+
+[*]
+indent_size = 2
+indent_style = space

.eslintrc

@@ -4,3 +4,4 @@ coverage/
 .nyc_output/
 dist/
 experiments/
+.rpt2_cache

.flowconfig

@@ -0,0 +1,10 @@
+{
+  "threshold": 0,
+  "reporters": [
+    "console"
+  ],
+  "absolute": true,
+  "format": [
+    "typescript"
+  ]
+}