refactor: use ES modules

- [x] convert require to import and module.exports to exports
- [x] docs: convert example to esm
- [x] docs: fix examples
- [x] docs: aggregate instancing/batching/shadows example
- [x] fix: handle buffer.length for ArrayBuffer
- [x] fix: debug not working in esm
- [x] fix(webgl2): use gl.MAX_COLOR_ATTACHMENTS instead of "MAX_COLOR_ATTACHMENTS"
- [x] fix(webgl2): handle EXT_disjoint_timer_query_webgl2
- [x] feat: add width/height getters
- [x] feat: set type to webgl2 #114

Closes #66
Closes #38

BREAKING CHANGE: switch to type module

.gitignore

@@ -1,6 +1,6 @@
-.DS_Store
 node_modules
-experiments
-.tern-port
+.DS_Store
+types
+lib
 examples/screenshots/*-diff.png
 examples/build/*

.npmignore

@@ -1,7 +1,10 @@
-.DS_Store
-node_modules
+web_modules
 examples
-experiments
 docs
-design
-.tern-port
+coverage
+test
+.github
+screenshot.*
+index.html
+tsconfig.json
+.editorconfig