ci: Add luacheck ci job (#317)

* Add luacheck ci job

* Fix most of the linting issues

* fixup: lint

Co-authored-by: TJ DeVries <devries.timothyj@gmail.com>

.luacheckrc

@@ -0,0 +1,26 @@
+-- Rerun tests only if their modification time changed.
+cache = true
+
+std = luajit
+codes = true
+
+self = false
+
+-- Glorious list of warnings: https://luacheck.readthedocs.io/en/stable/warnings.html
+ignore = {
+  "212", -- Unused argument, In the case of callback function, _arg_name is easier to understand than _, so this option is set to off.
+  "122", -- Indirectly setting a readonly global
+}
+
+globals = {
+  "TelescopeGlobalState",
+  "TelescopeCachedUppers",
+  "TelescopeCachedTails",
+  "TelescopeCachedNgrams",
+  "_TelescopeConfigurationValues",
+}
+
+-- Global objects defined by the C code
+read_globals = {
+  "vim",
+}