tweak folder structure

[0xa3k5]

• create a new "Best Practices" folder under the Subgraphs and move the best practice pages to that folder. (these pages were under subgraphs > cookbooks)
• rename the Best Practice pages' sidebar title to not include the "Best Practice 1/2/3/4/5/6 in them. (Best Practices 1: Pruning with indexerHints -> Pruning with indexerHints etc)
• slightly widen the sidebar width
• rename "Release Notes and Upgrade Guides" to Migration Guides (there is only 2 pages under that folder and both of them mentions migration guides instead of upgrade guides)
• move Subgraph Studio FAQ to Resources section (was under the Subgraphs > Developing > Deploying (I thought its better under resources because it was previously very buried and looks like its more general FAQ than just deploying)
• Slightly shorten a few sidebar titles (while keeping the titles meaningful and respected to how it was before)

[benface]

Thanks so much AK, and sorry I didn't figure out how to keep your commits. 😅 Superseded by #885