updating docs

usage/lua.md

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+
+## Basic example
+Given a sample.yml file of:
+```yaml
+---
+country: Australia # this place
+cities:
+- Sydney
+- Melbourne
+- Brisbane
+- Perth
+```
+then
+```bash
+yq -o=lua '.' sample.yml
+```
+will output
+```lua
+return {
+	["country"] = "Australia"; -- this place
+	["cities"] = {
+		"Sydney",
+		"Melbourne",
+		"Brisbane",
+		"Perth",
+	};
+};
+```
+
+## Unquoted keys
+Uses the `--lua-unquoted` option to produce a nicer-looking output.
+
+Given a sample.yml file of:
+```yaml
+---
+country: Australia # this place
+cities:
+- Sydney
+- Melbourne
+- Brisbane
+- Perth
+```
+then
+```bash
+yq -o=lua --lua-unquoted '.' sample.yml
+```
+will output
+```lua
+return {
+	country = "Australia"; -- this place
+	cities = {
+		"Sydney",
+		"Melbourne",
+		"Brisbane",
+		"Perth",
+	};
+};
+```
+
+## Globals
+Uses the `--lua-globals` option to export the values into the global scope.
+
+Given a sample.yml file of:
+```yaml
+---
+country: Australia # this place
+cities:
+- Sydney
+- Melbourne
+- Brisbane
+- Perth
+```
+then
+```bash
+yq -o=lua --lua-globals '.' sample.yml
+```
+will output
+```lua
+country = "Australia"; -- this place
+cities = {
+	"Sydney",
+	"Melbourne",
+	"Brisbane",
+	"Perth",
+};
+```
+
+## Elaborate example
+Given a sample.yml file of:
+```yaml
+---
+hello: world
+tables:
+  like: this
+  keys: values
+  ? look: non-string keys
+  : True
+numbers:
+  - decimal: 12345
+  - hex: 0x7fabc123
+  - octal: 0o30
+  - float: 123.45
+  - infinity: .inf
+  - not: .nan
+
+```
+then
+```bash
+yq -o=lua '.' sample.yml
+```
+will output
+```lua
+return {
+	["hello"] = "world";
+	["tables"] = {
+		["like"] = "this";
+		["keys"] = "values";
+		[{
+			["look"] = "non-string keys";
+		}] = true;
+	};
+	["numbers"] = {
+		{
+			["decimal"] = 12345;
+		},
+		{
+			["hex"] = 0x7fabc123;
+		},
+		{
+			["octal"] = 24;
+		},
+		{
+			["float"] = 123.45;
+		},
+		{
+			["infinity"] = (1/0);
+		},
+		{
+			["not"] = (0/0);
+		},
+	};
+};
+```
+