Add imgui versions v1.91.7 and v1.91.8

[AidanSun05]

No description provided.

[qudix]

Just add v1.91.8, there's no need to add the intermediary versions as I don't think CI will test those, only the latest.

[AidanSun05]

I think the CI should be testing everything, in the logs (like from build (ubuntu-latest, shared, release) for example) it contains these lines:

[...]
  => install imgui v1.91.8 .. ok
[...]
  => install imgui#1 v1.91.7 .. ok
[...]
  => install imgui#2 v1.91.8-docking .. ok
[...]
  => install imgui#3 v1.91.7-docking .. ok

[star-hengxing]

Just add v1.91.8, there's no need to add the intermediary versions as I don't think CI will test those, only the latest.

xmake-repo/scripts/test.lua

Lines 267 to 286 in cf1cdfe

	for _, line in ipairs(diff:split("\n")) do
	if line:startswith("+++ b/") then
	local file = line:sub(7)
	if file:startswith("packages") then
	assert(file == file:lower(), "%s must be lower case!", file)
	local package = file:match("packages/%w/(%S-)/")
	table.insert(packages, package)
	end
	elseif line:startswith("+") and line:find("add_versions") then
	local version = line:match("add_versions%(\"(.-)\"")
	if version:find(":", 1, true) then
	version = version:split(":")[2]
	end
	if #packages > 0 and version then
	local lastpackage = packages[#packages]
	local splitinfo = lastpackage:split("%s+")
	table.insert(packages, splitinfo[1] .. " " .. version)
	end
	end
	end

The test script will find all add_versions strings in the git diff.