edit_snippet_func: also present load_ft_func-filetypes.

Maybe it should even exclusively consider load_ft_func-filetypes, since
the intent of the function, at least as I see it, is to add a snippet to
any filetype for this buffer, and thats exactly the association
load_ft_func is supposed to model.

lua/luasnip/loaders/init.lua

@@ -1,5 +1,6 @@
 local Cache = require("luasnip.loaders._caches")
 local util = require("luasnip.util.util")
+local loader_util = require("luasnip.loaders.util")
 local Path = require("luasnip.util.path")
 
 local M = {}
@@ -93,8 +94,13 @@ function M.edit_snippet_files(opts)
 
 	local ft_filter = opts.ft_filter or util.yes
 
+	local all_fts = {}
+	vim.list_extend(all_fts, util.get_snippet_filetypes())
+	vim.list_extend(all_fts, loader_util.get_load_fts(vim.api.nvim_get_current_buf()))
+	all_fts = util.deduplicate(all_fts)
+
 	local filtered_fts = {}
-	for _, ft in ipairs(util.get_snippet_filetypes()) do
+	for _, ft in ipairs(all_fts) do
 		if ft_filter(ft) then
 			table.insert(filtered_fts, ft)
 		end