ESLint Improvements

[lishaduck]

Our ESLint configuration is loosely based on XO.

We should first review what configurations are unnecessary and remove them.

Then, there are a bunch of disabled lint rules.

• @typescript-eslint/no-unsafe-* (mostly blocked on Support for JSDoc type assertions typescript-eslint/typescript-eslint#1682) (Better TS #302)
• Rules about abusing promises
• Potential security issues
• unicorn/no-null
• unicorn/prevent-abbreviations (needs a lot of configuration to prevent changing src, etc in variable names)

Next, some tseslint tweaks might be helpful

• We should enable the recommended-strict tseslint rules
• Also, strict-boolean-expressions is nice
• We may wish to consider prefer-readonly
• ban-ts-comment could use some configuring from the default (Standardize comments #217)

Finally, we should consider if these other plugins would be useful:

• Add eslint-plugin-perfectionist? (~helps object monomorphization, which should help perf very slightly)
• Add eslint-plugin-no-use-extend-native to prevent messing with messed up prototypes (from XO)
• Add eslint-plugin-import-x a faster eslint-plugin-import with fewer dependencies (the original is in XO)