😒 chore(README): Link to main branch.

README.md

@@ -1,7 +1,7 @@
 [@aureooms/js-fingertree](https://aureooms.github.io/js-fingertree)
 ==
 
-<img src="https://cdn.rawgit.com/aureooms/js-fingertree/master/media/sketch.svg" width="864">
+<img src="https://cdn.rawgit.com/aureooms/js-fingertree/main/media/sketch.svg" width="864">
 
 Finger trees for JavaScript.
 See [docs](https://aureooms.github.io/js-fingertree).
@@ -11,17 +11,17 @@ Parent is [@aureooms/js-persistent](https://github.com/aureooms/js-persistent).
                       | Single x
                       | Deep ( Digit x ) ( FingerTree ( Node x ) ) ( Digit x )
 
-[![License](https://img.shields.io/github/license/aureooms/js-fingertree.svg)](https://raw.githubusercontent.com/aureooms/js-fingertree/master/LICENSE)
+[![License](https://img.shields.io/github/license/aureooms/js-fingertree.svg)](https://raw.githubusercontent.com/aureooms/js-fingertree/main/LICENSE)
 [![Version](https://img.shields.io/npm/v/@aureooms/js-fingertree.svg)](https://www.npmjs.org/package/@aureooms/js-fingertree)
-[![Build](https://img.shields.io/travis/aureooms/js-fingertree/master.svg)](https://travis-ci.org/aureooms/js-fingertree/branches)
+[![Build](https://img.shields.io/travis/aureooms/js-fingertree/main.svg)](https://travis-ci.org/aureooms/js-fingertree/branches)
 [![Dependencies](https://img.shields.io/david/aureooms/js-fingertree.svg)](https://david-dm.org/aureooms/js-fingertree)
 [![Dev dependencies](https://img.shields.io/david/dev/aureooms/js-fingertree.svg)](https://david-dm.org/aureooms/js-fingertree?type=dev)
 [![GitHub issues](https://img.shields.io/github/issues/aureooms/js-fingertree.svg)](https://github.com/aureooms/js-fingertree/issues)
 [![Downloads](https://img.shields.io/npm/dm/@aureooms/js-fingertree.svg)](https://www.npmjs.org/package/@aureooms/js-fingertree)
 
 [![Code issues](https://img.shields.io/codeclimate/issues/aureooms/js-fingertree.svg)](https://codeclimate.com/github/aureooms/js-fingertree/issues)
 [![Code maintainability](https://img.shields.io/codeclimate/maintainability/aureooms/js-fingertree.svg)](https://codeclimate.com/github/aureooms/js-fingertree/trends/churn)
-[![Code coverage (cov)](https://img.shields.io/codecov/c/gh/aureooms/js-fingertree/master.svg)](https://codecov.io/gh/aureooms/js-fingertree)
+[![Code coverage (cov)](https://img.shields.io/codecov/c/gh/aureooms/js-fingertree/main.svg)](https://codecov.io/gh/aureooms/js-fingertree)
 [![Code technical debt](https://img.shields.io/codeclimate/tech-debt/aureooms/js-fingertree.svg)](https://codeclimate.com/github/aureooms/js-fingertree/trends/technical_debt)
 [![Documentation](https://aureooms.github.io/js-fingertree/badge.svg)](https://aureooms.github.io/js-fingertree/source.html)
 [![Package size](https://img.shields.io/bundlephobia/minzip/@aureooms/js-fingertree)](https://bundlephobia.com/result?p=@aureooms/js-fingertree)
@@ -234,6 +234,6 @@ let right = tree.dropUntil( measure => measure > 2 ) ;
 ## References
 
   - [Hinze and Paterson](http://staff.city.ac.uk/~ross/papers/FingerTree.pdf)
-  - [An (incomplete) implementation in Python](https://github.com/kachayev/fn.py/blob/master/fn/immutable/finger.py)
+  - [An (incomplete) implementation in Python](https://github.com/kachayev/fn.py/blob/main/fn/immutable/finger.py)
   - [A (buggy) previous JavaScript implementation](https://github.com/qiao/fingertree.js)
-  - [A coffeescript implementation](https://github.com/zot/Leisure/blob/master/src/lib/fingertree.coffee)
+  - [A coffeescript implementation](https://github.com/zot/Leisure/blob/main/src/lib/fingertree.coffee)