feat(gitsigns): new keymap for Gitsigns blame (#3758)

Also add filetype `gitsigns.blame` to autocmd `lazyvim_close_with_q` and
workaround for `+hunks` group name to show prefix correctly. If you
don't like the workaround for `+hunks` group name feel free to remove
it.

## What is this PR for?
Make use of the new `gitsigns` feature `Gitsigns blame`, which shows in
a vertical buffer split the `blame` history of the whole buffer.
<!-- Describe the big picture of your changes to communicate to the
maintainers
  why we should accept this pull request. -->

## Does this PR fix an existing issue?
No.
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  If this PR fixes any issues, please link to the issue here.
  Fixes #<issue_number>
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## Checklist

- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.

lua/lazyvim/config/autocmds.lua

@@ -67,6 +67,7 @@ vim.api.nvim_create_autocmd("FileType", {
     "neotest-summary",
     "neotest-output-panel",
     "dbout",
+    "gitsigns.blame",
   },
   callback = function(event)
     vim.bo[event.buf].buflisted = false

lua/lazyvim/plugins/editor.lua

@@ -177,7 +177,7 @@ return {
         ["<leader>c"] = { name = "+code" },
         ["<leader>f"] = { name = "+file/find" },
         ["<leader>g"] = { name = "+git" },
-        ["<leader>gh"] = { name = "+hunks" },
+        ["<leader>gh"] = { name = "+hunks", ["_"] = "which_key_ignore" },
         ["<leader>q"] = { name = "+quit/session" },
         ["<leader>s"] = { name = "+search" },
         ["<leader>u"] = { name = "+ui" },
@@ -226,6 +226,7 @@ return {
         map("n", "<leader>ghR", gs.reset_buffer, "Reset Buffer")
         map("n", "<leader>ghp", gs.preview_hunk_inline, "Preview Hunk Inline")
         map("n", "<leader>ghb", function() gs.blame_line({ full = true }) end, "Blame Line")
+        map("n", "<leader>ghB", function() gs.blame() end, "Blame Buffer")
         map("n", "<leader>ghd", gs.diffthis, "Diff This")
         map("n", "<leader>ghD", function() gs.diffthis("~") end, "Diff This ~")
         map({ "o", "x" }, "ih", ":<C-U>Gitsigns select_hunk<CR>", "GitSigns Select Hunk")