Fix page break and header texts

[Ugboaja-Uchechi]

What kind of change does this PR introduce?

A bugfix

Issue Number:

Fixes issue #485

Snapshots/Videos:

Before	After

Summary

• In this PR I fixed the page break in the "plugin-architecture" page.
• I also adjusted the font-size of the h2 and h3 tags because of how similar they looked so as to make a clear hierarchy of different headers to make it easier for users to differentiate different headings.

Does this PR introduce a breaking change?

No

Other information

Have you read the contributing guide?

[Biki-das]

hey @Ugboaja-Uchechi could you remove that yarn.lock change!