Language Server
---------------

1. Identifies links and imports so the editor can mark
   them as such.  Ctrl+click on the links will attempt
   to launch what the link points to.
2. 'Find All References' will show a list (as presented
    by vscode) of all references of the given node.
3. 'Goto Definition' will do one of two things.  If there
    are multiple definitions, it will show a list similar
    to 'Find All References'.  If there is only one option
    for the definition, then the cursor will jump to that
    option.
4. 'Rename...' will rename a node.  If there are multiple
    nodes (a.style... / a.shape... / a.lable... / etc.),
    then a rename will change all locations that contain
    that node.
5. Auto Completion:
    a) Typing a '@' will show a list of d2 files that are contained in the d2 documents current folder and all child folders from there.
    b) Typing a '.' that is along a valid path, will bring up the proper list for that position in the path.
    c) Typing a ':' will bring up a list of possible values for that position in the current path.  If there is no list, in the case of a freeform field such as 'label', then no list is shown.
    d) The 'Tab' key will commit the auto completion.
6. When a preview is not present, then there is no error
   messages generated, the language server will show any
   errors that are created during the AST phase of d2
   compliation.

 into LanguageServer

New items in the PR

To facilitate a better edit/build/debug process, the extenstion was moved to a 'client' directory, the language server to a 'server' directory. **_Note:_** This may break the nightly build process and will need to be ajusted.

1. Identifies links and imports so the editor can mark
   them as such. Ctrl+click on the links will attempt
   to launch what the link points to.
2. 'Find All References' will show a list (as presented
   by vscode) of all references of the given node.
3. 'Goto Definition' will do one of two things. If there
   are multiple definitions, it will show a list similar
   to 'Find All References'. If there is only one option
   for the definition, then the cursor will jump to that
   option.
4. 'Rename...' will rename a node. If there are multiple
   nodes (a.style... / a.shape... / a.label... / etc.),
   then a rename will change all locations that contain
   that node.
5. Auto Completion:

    a) Typing a '@' will show a list of d2 files that are contained in the d2 documents current folder and all child folders from there.

    b) Typing a '.' that is along a valid path, will bring up the proper list for that position in the path.

    c) Typing a ':' will bring up a list of possible values for that position in the current path. If there is no list, in the case of a freeform field such as 'label', then no list is shown.

    d) The 'Tab' key will commit the auto completion.
6. When a preview is not present, then there is no error messages generated, the language server will show any errors that are created during the AST phase of d2 compliation.

 into LanguageServer

Fixes terrastruct#133