Feature request: searchable syntax help for PCB Editor DRC Rules

Description

The 'Syntax Help' dialog is helpful to consult when writing custom design rules, however it would be even more helpful if it had a text search or index feature, so that commands could be easier to look up. Alternatively, a more prominently located link to the web documentation (which is currently at the bottom of the text) might also be fine, since most of the other KiCad help menus seems to redirect to online sources.

Steps to reproduce

1. Open any project, then open the PCB editor
2. Open the board select menu, and select the 'Design Rules'->'Custom Rules' page
3. Click the 'Syntax help' shortcut in the top right corner
4. A dialog box opens up with all of the design rules syntax, but with no way to interact with it besides scrolling

KiCad Version

Application: KiCad PCB Editor x64 on x64

Version: 9.0.4, release build

Libraries:
	wxWidgets 3.2.8
	FreeType 2.13.3
	HarfBuzz 10.2.0
	FontConfig 2.15.0
	libcurl/8.13.0-DEV Schannel zlib/1.3.1

Platform: Windows 10 (build 19045), 64-bit edition, 64 bit, Little endian, wxMSW
OpenGL: NVIDIA Corporation, NVIDIA GeForce GTX 1080/PCIe/SSE2, 4.6.0 NVIDIA 576.52

Build Info:
	Date: Aug 18 2025 00:41:45
	wxWidgets: 3.2.8 (wchar_t,wx containers)
	Boost: 1.88.0
	OCC: 7.9.1
	Curl: 8.13.0-DEV
	ngspice: 44
	Compiler: Visual C++ 1942 without C++ ABI
	KICAD_IPC_API=ON

Locale: 
	Lang: en_US
	Enc: UTF-8
	Num: 1,234.5
	Encoded кΩ丈: D0BACEA9E4B888 (sys), D0BACEA9E4B888 (utf8)