Restructure project directories (#333)

`/client/web` -> `/frontend`
`/client/cli` -> *delete for now*
`/client/native` -> *delete for now*
`/core/editor` -> `/editor`
`/core/document` -> `/graphene`
`/core/renderer` -> `/charcoal`
`/core/proc-macro` -> `/proc-macros` *(now plural)*

frontend/assets/16px-solid/eye-visible.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16">
+	<path d="M8,3C3,3,0,8,0,8s3,5,8,5s8-5,8-5S13,3,8,3z M8,12c-2.2,0-4-1.8-4-4s1.8-4,4-4s4,1.8,4,4S10.2,12,8,12z" />
+	<circle cx="9" cy="7" r="1.2" />
+</svg>