feat(providers): Inital COC support

Closes #68
Still needs support for code actions/hover/rename etc

lua/symbols-outline/providers/init.lua

@@ -2,9 +2,24 @@ local M = {}
 
 local providers = {
     'symbols-outline/providers/nvim-lsp',
+    'symbols-outline/providers/coc',
     'symbols-outline/providers/markdown'
 }
 
+local current_provider;
+
+function M.has_provider()
+    local ret = false;
+    for _, value in ipairs(providers) do
+       local provider = require(value)
+       if provider.should_use_provider(0) then
+           ret = true;
+           break
+       end
+    end
+    return ret
+end
+
 ---@param on_symbols function
 function M.request_symbols(on_symbols)
    for _, value in ipairs(providers) do