Website integration (#365)

docs/README.md

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+The `Athena::Negotiation` component allows an application to support [content negotiation](https://tools.ietf.org/html/rfc7231#section-5.3).
+The component has no dependencies and is framework agnostic; supporting various negotiators.
+
+## Installation
+
+First, install the component by adding the following to your `shard.yml`, then running `shards install`:
+
+```yaml
+dependencies:
+  athena-negotiation:
+    github: athena-framework/negotiation
+    version: ~> 0.1.0
+```
+
+## Usage
+
+The main type of [Athena::Negotiation][] is [ANG::AbstractNegotiator][] which is used to implement negotiators for each `Accept*` header.
+`Athena::Negotiation` exposes class level getters for each negotiator; that return a lazily initialized singleton instance.
+Each negotiator exposes two methods: [ANG::AbstractNegotiator#best][] and [ANG::AbstractNegotiator#ordered_elements][].
+
+### Media Type
+
+```crystal
+negotiator = ANG.negotiator
+
+accept_header = "text/html, application/xhtml+xml, application/xml;q=0.9"
+priorities = ["text/html; charset=UTF-8", "application/json", "application/xml;q=0.5"]
+
+accept = negotiator.best(accept_header, priorities).not_nil!
+
+accept.media_range # => "text/html"
+accept.parameters  # => {"charset" => "UTF-8"}
+```
+
+The [ANG::Negotiator][] type returns an [ANG::Accept][], or `nil` if negotiating the best media type has failed.
+
+### Character Set
+
+```crystal
+negotiator = ANG.charset_negotiator
+
+accept_header = "ISO-8859-1, UTF-8; q=0.9"
+priorities = ["iso-8859-1;q=0.3", "utf-8;q=0.9", "utf-16;q=1.0"]
+
+accept = negotiator.best(accept_header, priorities).not_nil!
+
+accept.charset # => "utf-8"
+accept.quality # => 0.9
+```
+
+The [ANG::CharsetNegotiator][] type returns an [ANG::AcceptCharset][], or `nil` if negotiating the best character set has failed.
+
+### Encoding
+
+```crystal
+negotiator = ANG.encoding_negotiator
+
+accept_header = "gzip;q=1.0, identity; q=0.5, *;q=0"
+priorities = ["gzip", "foo"]
+
+accept = negotiator.best(accept_header, priorities).not_nil!
+
+accept.coding # => "gzip"
+```
+
+The [ANG::EncodingNegotiator][] type returns an [ANG::AcceptEncoding][], or `nil` if negotiating the best encoding has failed.
+
+### Language
+
+```crystal
+negotiator = ANG.language_negotiator
+
+accept_header = "en; q=0.1, fr; q=0.4, zh-Hans-CN; q=0.9, de; q=0.2"
+priorities = ["de", "zh-Hans-CN", "en"]
+
+accept = negotiator.best(accept_header, priorities).not_nil!
+
+accept.language # => "zh"
+accept.region   # => "cn"
+accept.script   # => "hans"
+```
+
+The [ANG::LanguageNegotiator][] type returns an [ANG::AcceptLanguage][], or `nil` if negotiating the best language has failed.