chore(vimdoc): Auto update

doc/outline.txt

@@ -448,12 +448,13 @@ External providers: - Asciidoc
 <https://github.com/msr1k/outline-asciidoc-provider.nvim> (no external
 requirements)
 
+How to implement an external provider ~
 
-EXTERNAL PROVIDERS ~
-
-External providers can be appended to the `providers.priority` list. Each item
-in the list is appended to `"outline.providers.<item>"` to form an import path,
-for use as a provider.
+External providers are separate plugins that users can install in addition to
+`outline.nvim`. Their names can be appended to the `providers.priority` list in
+the outline.nvim config. Each item in the `providers.priority` list is used to
+form an import path `"outline.providers.<item>"` and then `require()`’ed for
+use as a provider.
 
 External providers from plugins should define the provider module at
 `lua/outline/providers/<name>.lua` with these functions:
@@ -472,14 +473,15 @@ External providers from plugins should define the provider module at
     - param `callback` is a function that receives a list of symbols and the
         `opts` table.
     - param `opts` can be passed to `callback` without processing
-    Each symbol table in the list of symbols should have these fields:
-    - name: string
-    - kind: integer
+    The function should return a list of "symbol tables".
+    Each symbol table should have these fields:
+    - name: string – displayed in the outline
+    - kind: integer – determines the icon to use
     - selectionRange: table with fields `start` and `end`, each have fields
-        `line` and `character`, each integers
-    - range: table with fields `start` and `end`, each have fields `line` and
-        `character`, each integers
-    - children: list of table of symbols
+        `line` and `character`, each integers:
+        `{ start = { line = ?, character = ? }, ['end'] = { line = ?, character = ? } }`
+    - range: same as selectionRange
+    - children: list of symbol tables
     - detail: (optional) string, shown for `outline_items.show_symbol_details`
 
 The built-in markdown <./lua/outline/providers/markdown.lua> provider is a good
@@ -488,8 +490,8 @@ and uses regex; the built-in norg <./lua/outline/providers/norg.lua> provider
 is an example which uses treesitter.
 
 All providers should support at least nvim 0.7. You can make use of
-`_G._outline_nvim_has` with fields `[8]` and `[9]` equivalent to
-`vim.fn.has('nvim-0.8') == 1` and `vim.fn.has('nvim-0.9') == 1` respectively.
+`_G._outline_nvim_has` with fields `[8]`, `[9]`, and `[10]`. For instance,
+`_G._outline_nvim_has[8]` is equivalent to: `vim.fn.has('nvim-0.8') == 1`.
 
 If a higher nvim version is required, it is recommended to check for this
 requirement in the `supports_buffer` function.