Update doc for statusline (#3665)

docs/cn/documentation.md

@@ -648,6 +648,24 @@ endfunction
     ]
 ```
 
+**自定义板块**
+
+可以使用启动函数添加自定板块，比如：
+
+```vim
+function! s:test_section() abort
+  return 'ok'
+endfunction
+call SpaceVim#layers#core#statusline#register_sections('test', function('s:test_section'))
+```
+
+之后就可以在配置文件中添加 `test` 板块，比如，在状态栏右侧最后添加：
+
+```toml
+[options]
+    statusline_right_sections = ['cursorpos', 'percentage', 'test']
+```
+
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docs/documentation.md

@@ -674,17 +674,36 @@ switching between different colorschemes, you may need to set
 `custom_color_palette` in your custom configuration file. For example:
 
 ```toml
-custom_color_palette = [
-["#282828", "#a89984", 246, 235],
-["#a89984", "#504945", 239, 246],
-["#a89984", "#3c3836", 237, 246],
-["#665c54", 241],
-["#282828", "#83a598", 235, 109],
-["#282828", "#fe8019", 235, 208],
-["#282828", "#8ec07c", 235, 108],
-["#282828", "#689d6a", 235, 72],
-["#282828", "#8f3f71", 235, 132],
-]
+[options]
+    custom_color_palette = [
+        ["#282828", "#a89984", 246, 235],
+        ["#a89984", "#504945", 239, 246],
+        ["#a89984", "#3c3836", 237, 246],
+        ["#665c54", 241],
+        ["#282828", "#83a598", 235, 109],
+        ["#282828", "#fe8019", 235, 208],
+        ["#282828", "#8ec07c", 235, 108],
+        ["#282828", "#689d6a", 235, 72],
+        ["#282828", "#8f3f71", 235, 132],
+    ]
+```
+
+**Custion section**
+
+You can use bootstrap function to add custom section to statusline, for example:
+
+```vim
+function! s:test_section() abort
+  return 'ok'
+endfunction
+call SpaceVim#layers#core#statusline#register_sections('test', function('s:test_section'))
+```
+
+Then, add `test` section to `statusline_right_sections` option:
+
+```toml
+[options]
+    statusline_right_sections = ['cursorpos', 'percentage', 'test']
 ```
 
 ### Tabline