A bit typos in manual

[XAjzh]

I am a beginner to TikZ. When I read the pgfmanual, I found a bit typos. Then I read the latest pgfmanual which is on https://pgf-tikz.github.io/pgf/pgfmanual.pdf and https://github.com/pgf-tikz/pgf/releases. The typos still exist.

All the typos are library's name. They are listed below with bold style(copy from https://pgf-tikz.github.io/pgf/pgfmanual.pdf).

part 1, section 3 Tutorial: A Petri-Net for Hagen, subsection 3.13 Using Layers: The Background Rectangles, second paragraph:

The solution is to use layers. When the background library is loaded, Hagen can put parts of his picture inside a scope with the on background layer option...

part 1, section 5 Tutorial: Diagrams as Simple Graphs, subsection 5.4 The Diagram as a Graph:

Matrices allow Ilka to align the nodes nicely, but the connections are not quite perfect. The problem is that the code does not really reflect the paths that underlie the diagram. For this, it seems natural enough to Ilka to use the graph library since, after all, connecting nodes by edges is exactly what happens in a graph. The graph library can both be used to connect nodes that have already been created, but it can also be used to create nodes “on the fly” and these processes can also be mixed.

Help this helps. Then, please don't mind my poor English.

Thank you for your work.