chore: Update Luacheck CI action and check for minimum Luua version

See related commits in
Omikhleia/markdown.sile#101

Co-authored-by: Caleb Maclennan <caleb@alerque.com>

.github/workflows/luacheck.yml

@@ -8,6 +8,6 @@ jobs:
     runs-on: ubuntu-22.04
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Luacheck
-        uses: lunarmodules/luacheck@v0
+        uses: lunarmodules/luacheck@v1

.luacheckrc

@@ -1,4 +1,4 @@
-std = "max"
+std = "min+sile"
 include_files = {
   "**/*.lua",
   "sile.in",
@@ -19,15 +19,6 @@ exclude_files = {
 files["**/*_spec.lua"] = {
   std = "+busted"
 }
-globals = {
-  "SILE",
-  "SU",
-  "luautf8",
-  "pl",
-  "fluent",
-  "SYSTEM_SILE_PATH",
-  "SHARED_LIB_EXT"
-}
 max_line_length = false
 ignore = {
   "581" -- operator order warning doesn't account for custom table metamethods