Present aiken-lsp & fill-in CHANGELOG

crates/aiken-lsp/README.md

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+# Aiken Language Server Protocol (LSP)
+
+The `aiken` command-line comes built-in with a _Language Server_ implementing
+(part of) the [Language Server Protocol](https://microsoft.github.io/language-server-protocol/).
+
+## Getting Started
+
+### General
+
+Regardless of your IDE, you'll likely need the following information to configure your language client:
+
+- command: `aiken lsp`
+  > **Note**
+  > The command is hidden from the command-line help usage
+
+- root pattern: `aiken.toml`
+- filetype: `aiken` `(.ak)`
+
+### VsCode
+
+Simply install the [VSCode Aiken extension](https://marketplace.visualstudio.com/items?itemName=TxPipe.aiken) from the official marketplace.
+
+### NeoVim
+
+If you're using NeoVim and using [`nvim-lspconfig`](https://github.com/neovim/nvim-lspconfig) then there's almost
+nothing to do as Aiken is directly supported. Simply follow the [official
+instructions](https://github.com/neovim/nvim-lspconfig/blob/master/doc/server_configurations.md#aiken)
+
+## Supported Capabilities
+
+- [x] Document syncing and on-the-fly compilation
+- [x] Document formatting (akin to `aiken fmt`)
+- [x] Go-to definition
+- [x] Type annotation on hover
+- [x] Code actions providing quickfixes for a variety of errors:
+    - [x] `aiken::check::unknown::variable`
+    - [x] `aiken::check::unknown::type`
+    - [x] `aiken::check::unknown::type_constructor`
+    - [x] `aiken::check::unknown::module`