nvim: Add prose headline highlighting

Added simple highlighting plugin for prose headlines (and code
snippets). Will highlight the whole line a little from the
background and provide more space around it so it stands out.

Currently works (afaik) for markdown, rmd, norg filetypes.

nvim/.config/nvim/lazy-lock.json

@@ -28,6 +28,7 @@
   "friendly-snippets": { "branch": "main", "commit": "ea84a710262cb2c286d439070bad37d36fd3db25" },
   "fwatch.nvim": { "branch": "main", "commit": "a691f7349dc66285cd75a1a698dd28bca45f2bf8" },
   "gitsigns.nvim": { "branch": "main", "commit": "bb808fc7376ed7bac0fbe8f47b83d4bf01738167" },
+  "headlines.nvim": { "branch": "master", "commit": "ddef41b2664f0ce25fe76520d708e2dc9dfebd70" },
   "jupyter-kernel.nvim": { "branch": "main", "commit": "5b409598033884a3d819e2a3bcd1fe340bc8d783" },
   "lazy.nvim": { "branch": "main", "commit": "b7303a68309296fb4809c51ce0bf66722e5dc4f7" },
   "lightspeed.nvim": { "branch": "main", "commit": "299eefa6a9e2d881f1194587c573dad619fdb96f" },

nvim/.config/nvim/lua/plugins/prose.lua

@@ -22,6 +22,13 @@ return {
 			})
 		end,
 	},
+	-- displays prettier headlines mimicking the ones in emacs orgmode
+	{
+		"lukas-reineke/headlines.nvim",
+		dependencies = "nvim-treesitter/nvim-treesitter",
+	    config = true,
+	    ft = writing_ft,
+	},
 	-- generate an auto-updating html preview for md files
 	{
 		"iamcco/markdown-preview.nvim",