Add support for ink-language-server

This commit add support for ink-language-server, which it does by
largely copying and pasting from the pure-language-server PR that was
merged recently.

The most interesting things to note are:
- ink-language-server is distributed upstream via npm, which is why we
  search through node_modules
- With some coaxing, it can be installed globally - which is why we
  search for a global binary.
- Ink is a funky language, and users will likely need to add
  initialization options.
- I am not incredibly familiar with vimscript; and I may not have done
  some of the buffer searching correctly.

doc/ale-ink.txt

@@ -0,0 +1,40 @@
+===============================================================================
+ALE Ink Integration                                           *ale-ink-options*
+
+
+===============================================================================
+ink-language-server                                   *ale-ink-language-server*
+
+Ink Language Server
+  (https://github.com/ephraim/ink-language-server)
+
+g:ale_ink_ls_executable                               g:ale_ink_ls_executable
+                                                      b:ale_ink_ls_executable
+  Type: |String|
+  Default: `'ink-language-server'`
+
+  Ink language server executable.
+
+g:ale_ink_ls_initialization_options
+                                          g:ale_ink_ls_initialization_options
+                                          b:ale_ink_ls_initialization_options
+  Type: |Dictionary|
+  Default: `{}`
+
+  Dictionary containing configuration settings that will be passed to the
+  language server at startup. For certain platforms and certain story
+  structures, the defaults will suffice. However, many projects will need to
+  change these settings - see the ink-language-server website for more
+  information.
+
+  An example of setting non-default options:
+		{
+		\  'ink': {
+		\    'mainStoryPath': 'init.ink',
+		\    'inklecateExecutablePath': '/usr/local/bin/inklecate',
+		\    'runThroughMono': v:false
+		\  }
+		\}
+
+===============================================================================
+  vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl:

doc/ale-supported-languages-and-tools.txt

@@ -198,6 +198,8 @@ Notes:
   * `write-good`
 * Idris
   * `idris`
+* Ink
+  * `ink-language-server`
 * ISPC
   * `ispc`!!
 * Java

doc/ale.txt

@@ -2123,6 +2123,8 @@ documented in additional help files.
     write-good............................|ale-html-write-good|
   idris...................................|ale-idris-options|
     idris.................................|ale-idris-idris|
+  ink.....................................|ale-ink-options|
+    ink-language-server...................|ale-ink-language-server|
   ispc....................................|ale-ispc-options|
     ispc..................................|ale-ispc-ispc|
   java....................................|ale-java-options|