feat: make Eslint use ECMA and module source type

[bytrangle]

Hey, thank you so much for making this amazing renderer for Notion content. I've noticed two hiccups with Eslint config that can be fixed quickly:

• It is currently in .src/ directory
• There's almost nothing in it yet

Not configuring the parser option to use "sourceType: module" may lead to this error: "The keyword ... is reserved", as discussed here.