tests: improve testing (#80)

* chore: setup mini.test

* chore(ci): setup new test runner, install plugin deps

* chore(ci): test only on stable and nightly releases

* test: iferr

* test: struct_tags

* test: impl

* test: gotests

lua/gopher/config.lua

@@ -23,7 +23,7 @@ local config = {}
 --minidoc_replace_start {
 
 ---@tag gopher.nvim-config-defaults
----@eval return MiniDoc.afterlines_to_code(MiniDoc.current.eval_section):gsub(">", ">lua")
+---@eval return MiniDoc.afterlines_to_code(MiniDoc.current.eval_section)
 ---
 ---@class gopher.Config
 local default_config = {