Auto generate vim docs

doc/symbols-outline.txt

@@ -273,6 +273,17 @@ Default values are shown:
         -- Symbols to ignore.
         -- Possible values are the Keys in the icons table below.
         blacklist = {},
+        -- Added in this fork:
+        -- You can use a custom function that returns the icon for each symbol kind.
+        -- This function takes a kind (string) as parameter and should return an
+        -- icon.
+        icon_fetcher = nil,
+        -- 3rd party source for fetching icons. Fallback if icon_fetcher returned
+        -- empty string. Currently supported values: 'lspkind'
+        icon_source = nil,
+        -- The next fall back if both icon_fetcher and icon_source has failed, is
+        -- the custom mapping of icons specified below. The icons table is also
+        -- needed for specifying hl group.
         -- Changed in this fork to fix deprecated icons not showing.
         icons = {
           File = { icon = "󰈔", hl = "@text.uri" },
@@ -317,6 +328,15 @@ To find out exactly what some of the options do, please see the
 |symbols-outline-recipes| section of the readme at the bottom for
 screen-recordings.
 
+The order in which the sources for icons are checked is:
+
+1. Icon fetcher function
+2. Icon source (only `lspkind` is supported for this option as of now)
+3. Icons table
+
+A fallback is always used if the previous candidate returned either an empty
+string or a falsey value.
+
 
 COMMANDS                                            *symbols-outline-commands*
 
@@ -404,6 +424,9 @@ Possible highlight groups provided by symbols-outline to customize:
 You can customize any other highlight groups using `winhl` too, this option is
 passed directly to the `winhl` vim option unprocessed.
 
+To customize colors of the symbol icons, use the `symbols.icons` table. See
+|symbols-outline-config|.
+
 
 PREVIEW WINDOW ~
 
@@ -461,6 +484,17 @@ TIPS                                                    *symbols-outline-tips*
 - To customize the background colors, text colors, and borders, you can use
     `outline_window.winhl` for the outline window or `preview_window.winhl` for the
     preview floating window. See |symbols-outline-highlights|.
+- To fix symbol icon related issues, there are several options. If you use
+    `lspkind`, you can set `symbols.icon_source = 'lspkind'` to use lspkind for
+    fetching icons. You can also use your own function `symbols.icon_fetcher` that
+    takes a string and should return an icon. Otherwise, you can edit the
+    `symbols.icons` table for specifying icons.
+    The order in which the sources of icons are checked is:
+    1. Icon fetcher function
+    2. Icon source
+    3. Icons table
+    A fallback is always used if the previous candidate returned either an empty
+    string or a falsey value.
 
 
 RECIPES                                              *symbols-outline-recipes*
@@ -560,6 +594,22 @@ the outline becomes more readable this way, hence this is an option.
 This feature is newly added in this fork, and is currently experimental (may be
 unstable).
 
+- **Custom icons**
+
+You can write your own function for fetching icons. Here is one such example
+that simply returns in plain text, the first letter of the given kind.
+
+>lua
+    symbols = {
+      icon_fetcher = function(kind) return kind:sub(1,1) end
+    }
+<
+
+The fetcher function, if provided, is checked first before using `icon_source`
+and `icons` as fallback.
+
+
+
 ==============================================================================
 1. Links                                               *symbols-outline-links*