feat(compose): new lib to compose functions

@vates/compose/README.md

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+<!-- DO NOT EDIT MANUALLY, THIS FILE HAS BEEN GENERATED -->
+
+# @vates/compose
+
+[![Package Version](https://badgen.net/npm/v/@vates/compose)](https://npmjs.org/package/@vates/compose) ![License](https://badgen.net/npm/license/@vates/compose) [![PackagePhobia](https://badgen.net/bundlephobia/minzip/@vates/compose)](https://bundlephobia.com/result?p=@vates/compose) [![Node compatibility](https://badgen.net/npm/node/@vates/compose)](https://npmjs.org/package/@vates/compose)
+
+> Compose functions from left to right
+
+## Install
+
+Installation of the [npm package](https://npmjs.org/package/@vates/compose):
+
+```
+> npm install --save @vates/compose
+```
+
+## Usage
+
+```js
+import { compose } from '@vates/compose'
+
+const add2 = x => x + 2
+const mul3 = x => x * 3
+
+// const f = x => mul3(add2(x))
+const f = compose(add2, mul3)
+
+console.log(f(5))
+// → 21
+```
+
+## Contributions
+
+Contributions are _very_ welcomed, either on the documentation or on
+the code.
+
+You may:
+
+- report any [issue](https://github.com/vatesfr/xen-orchestra/issues)
+  you've encountered;
+- fork and create a pull request.
+
+## License
+
+[ISC](https://spdx.org/licenses/ISC) © [Vates SAS](https://vates.fr)

@vates/compose/USAGE.md

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+```js
+import { compose } from '@vates/compose'
+
+const add2 = x => x + 2
+const mul3 = x => x * 3
+
+// const f = x => mul3(add2(x))
+const f = compose(add2, mul3)
+
+console.log(f(5))
+// → 21
+```

@vates/compose/index.js

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+'use strict'
+
+exports.compose = function compose(fns) {
+  if (!Array.isArray(fns)) {
+    fns = Array.from(arguments)
+  }
+  const n = fns.length
+  if (n === 0) {
+    throw new TypeError('at least one function must be passed')
+  }
+  if (n === 1) {
+    return fns[0]
+  }
+  return function (value) {
+    for (let i = 0; i < n; ++i) {
+      value = fns[i](value)
+    }
+    return value
+  }
+}

@vates/compose/index.spec.js

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+/* eslint-env jest */
+
+const { compose } = require('./')
+
+const add2 = x => x + 2
+const mul3 = x => x * 3
+
+describe('compose()', () => {
+  it('throws when no functions is passed', () => {
+    expect(() => compose()).toThrow(TypeError)
+    expect(() => compose([])).toThrow(TypeError)
+  })
+
+  it('applies from left to right', () => {
+    expect(compose(add2, mul3)(5)).toBe(21)
+  })
+
+  it('accepts functions in an array', () => {
+    expect(compose([add2, mul3])(5)).toBe(21)
+  })
+})

@vates/compose/package.json

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+{
+  "private": false,
+  "name": "@vates/compose",
+  "description": "Compose functions from left to right",
+  "homepage": "https://github.com/vatesfr/xen-orchestra/tree/master/@vates/compose",
+  "bugs": "https://github.com/vatesfr/xen-orchestra/issues",
+  "repository": {
+    "directory": "@vates/compose",
+    "type": "git",
+    "url": "https://github.com/vatesfr/xen-orchestra.git"
+  },
+  "author": {
+    "name": "Vates SAS",
+    "url": "https://vates.fr"
+  },
+  "license": "ISC",
+  "version": "0.0.0",
+  "engines": {
+    "node": ">=6.5"
+  },
+  "scripts": {
+    "postversion": "npm publish --access public"
+  }
+}