blogpost: Optimizing the code intelligence commit graph

Created by: efritz

This is the fourth article in a list of technical deep(-er) dives into code intelligence features. The other three were (fairly) well received and seems worth it to keep churning out content about it when it's interesting enough to write about.

For context the other three articles can be found here (some also linked within the article).

• The Language Server Index Format (LSIF) at Sourcegraph, a year in review
• Optimizing a code intelligence backend
• Optimizing a code intelligence indexer

This PR currently holds a rough first-draft that has all of the basic ideas down. There could be better ways to present some of the information or frame it as a slightly different narrative. I'm open to any structural suggestions at this point (as well as filling out the introduction or padding the end, which I haven't put too much effort into yet).