fix: a lot of small things and adds more customization for caret (#554)

Attention:
prompt_prefix will no longer add a space at the end. So if you still want a space at the end make sure your configuration has one.
The default should not be changed. So if you haven't copied prompt_prefix in your config this doesn't affect you.

Feat:
- prompt prefix does no longer always end with space
- selection_caret configurable. Default: `> `
- result_prefix configurable. Default: `  `
- more actions for git_branches
  - <c-t> does track the branch
  - <c-r> does rebase branch
  - also added delete branch action but not configured. See readme on how to do that

Fixes:
- fix docgen ci
- Better error for lsp_workspace_symbols
- better formatting for CONTRIBUTING.md
- move from systemlist to plenary.job
- git branch now supports checkout on remote branches

doc/telescope.txt

@@ -7,6 +7,11 @@ filter, find and pick things in Lua.
 To find out more:
 https://github.com/nvim-telescope/telescope.nvim
 
+  :h telescope.setup
+  :h telescope.builtin
+  :h telescope.layout
+  :h telescope.actions
+
 telescope.extensions()                                *telescope.extensions()*
 
     Use telescope.extensions to reference any extensions within your
@@ -43,6 +48,18 @@ telescope.setup({opts})                                    *telescope.setup()*
 
     Valid keys for {opts.defaults}
 
+                                          *telescope.defaults.entry_prefix*
+    entry_prefix: ~
+        Prefix in front of each result entry. Current selection not included.
+
+        Default: '  '
+
+                                         *telescope.defaults.prompt_prefix*
+    prompt_prefix: ~
+        Will be shown in front of the prompt.
+
+        Default: '> '
+
                                        *telescope.defaults.scroll_strategy*
     scroll_strategy: ~
         Determines what happens you try to scroll past view of the picker.
@@ -51,6 +68,12 @@ telescope.setup({opts})                                    *telescope.setup()*
           - "cycle" (default)
           - "limit"
 
+                                       *telescope.defaults.selection_caret*
+    selection_caret: ~
+        Will be shown in front of the selection.
+
+        Default: '> '
+
                                     *telescope.defaults.selection_strategy*
     selection_strategy: ~
         Determines how the cursor acts after each sort iteration.