Editor support generalized: shared core, language server, Vim and VS Code (from dev eb5baf9cbe59)

doc/edit/ now holds a shared Python implementation of the language's
structural layer (klammertext_edit.py) and a dependency-free language
server (klammertext_ls.py), with integrations for Emacs, Sublime Text,
Vim, and Visual Studio Code.  The editor test suite in tst/ covers the
core's API and CLI, the language server protocol, the VS Code
extension, headless Vim, and Emacs byte-equality.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

doc/edit/vscode/language-configuration.json

@@ -0,0 +1,11 @@
+{
+    "comments": {
+        "lineComment": "#",
+        "blockComment": ["#[", "]#"]
+    },
+    "brackets": [
+        ["#[", "]#"]
+    ],
+    "autoClosingPairs": [],
+    "surroundingPairs": []
+}