feat(builtins): add completion source for nvim-snippets

[przepompownia]

https://github.com/garymjr/nvim-snippets

[przepompownia]

I see that none-ls cannot recognize the prefix boundary if the snippet is prefixed with non-keyword character like this (/**):

https://github.com/rafamadriz/friendly-snippets/blob/de8fce94985873666bd9712ea3e49ee17aadb1ed/snippets/cpp/cppdoc.json#L20-L30

none-ls.nvim/lua/null-ls/utils/make_params.lua

Lines 62 to 68 in dcc8cd4

	local get_word_to_complete = function(params)
	local line = params.content[params.row]
	local line_to_cursor = line:sub(1, params.col)
	local regex = vim.regex("\\k*$")
	return line:sub(regex:match_str(line_to_cursor) + 1, params.col)
	end

[przepompownia]

Thanks to the case for /** prefix I noticed buggy filtering and fixed it with a separated regex stolen from cmp-luasnip and slightly modified. I'm not sure if such pattern should be hardcoded or configured per filetype. Maybe someone else can find some example, for which such hardcoded pattern is incorrect.

Expanding such snippets is longer incorrect. For /** */ and label (prefix) /** I get /**/** */), but I see that the same happens without none-ls (and needs the repro for clean Nvim). To show this behavior I modified locally my unmerged branch on Phpactor phpactor/phpactor#2622.

diff --git a/lib/Completion/Bridge/TolerantParser/WorseReflection/KeywordCompletor.php b/lib/Completion/Bridge/TolerantParser/WorseReflection/KeywordCompletor.php
index 37190f27..562c0c48 100644
--- a/lib/Completion/Bridge/TolerantParser/WorseReflection/KeywordCompletor.php
+++ b/lib/Completion/Bridge/TolerantParser/WorseReflection/KeywordCompletor.php
@@ -47,6 +47,7 @@ class KeywordCompletor implements TolerantCompletor
         'try' => " {\$3\n} catch (\${1:Exception} \\\$\${2:error}) {\$4\n}",
         'while' => " (\$1) {\$0\n}",
         'yield' => ' $1;$0',
+        '/**' => ' $1 */$0',
     ];

[przepompownia]

Full Nvim example: neovim/neovim#30905

[przepompownia]

Using textEdit allows to workaround non-keyword labels problem but not always: for example, if phpactor is attached to the PHP buffer too.