refactor(web): extensions array clean up, plugin usage and naming consistency

[HejSztynx]

Summary

• there was some inconsistency with plugin namings, as some used camelCase and some PascalCase, now every plugin is in PascalCase
• introduced inline *Plugin configurations, just like it was done in the latter Placeholder plugin for clarity and to get rid of useMemos and to shorten the dependency array
• unified custom plugin creations, now each one uses .configure() method

[HejSztynx]

The last commit solely introduces files and directory renamings, to make the pr easier to look at