resolve include file suggestions relative to document

[eiswind]

Description

autocomplete suggestions for include:: are currently resolved against the workspace root:

asciidoctor-vscode/src/providers/asciidoc.provider.ts

Lines 53 to 58 in b65f1c1

	const workspace = vscode.workspace.getWorkspaceFolder(context.document.uri)
	const rootPath = workspace?.uri.fsPath
	const searchPath = getPathOfFolderToLookupFiles(
	context.document.uri.fsPath,
	path.join(rootPath, entryDir)
	)

this works as long as all asciidoc files live in the root of the workspace. as soon as we place them in a subfolder, it is broken

Additional Context

I created a PR #618 that suggests resolving the files relative to the source document.

https://github.com/asciidoctor/asciidoctor-vscode/pull/618/files#diff-fb3632b9c41b259ca81bd1f9be15c3b88bd68efe5d88727117468c79e50fd720R53-R56

[ggrossetie]

fixed in #618