fix: Add treegrid as allowed parent to rowgroup (#1435)

`rowgroup` is allowed a `treegrid` context according to the [ARIA spec](https://www.w3.org/TR/wai-aria-1.1/#rowgroup).

Closes: #1386 

## Reviewer checks

**Required fields, to be filled out by PR reviewer(s)**
- [x] Follows the commit message policy, appropriate for next version
- [x] Has documentation updated, a DU ticket, or requires no documentation change
- [x] Includes new tests, or was unnecessary
- [x] Code is reviewed for security by: @WilcoFiers

Author: straker

lib/commons/aria/index.js

@@ -1653,7 +1653,7 @@ lookupTable.role = {
 			all: ['row']
 		},
 		nameFrom: ['author', 'contents'],
-		context: ['grid', 'table'],
+		context: ['grid', 'table', 'treegrid'],
 		implicit: ['tbody', 'thead', 'tfoot'],
 		unsupported: false
 	},

test/integration/rules/aria-required-parent/aria-required-parent.html

@@ -8,3 +8,6 @@
 <div role="listitem" id="fail3"></div>
 <div role="list" id="pass7" aria-owns="parent"></div>
 <div id="parent"><div role="listitem" id="pass8"></div></div>
+<div role="grid" id="pass9"><div role="rowgroup" id="pass10">Item 1</div></div>
+<div role="table" id="pass11"><div role="rowgroup" id="pass12">Item 1</div></div>
+<div role="treegrid" id="pass13"><div role="rowgroup" id="pass14">Item 1</div></div>

test/integration/rules/aria-required-parent/aria-required-parent.json

@@ -10,6 +10,12 @@
 		["#pass5"],
 		["#pass6"],
 		["#pass7"],
-		["#pass8"]
+		["#pass8"],
+		["#pass9"],
+		["#pass10"],
+		["#pass11"],
+		["#pass12"],
+		["#pass13"],
+		["#pass14"]
 	]
 }