feat(theme): make default icons overrideable

[Flachz]

Resolves #1354 Partially addresses #1578

This adds the option of overriding the default icons in theme.yml.

Example theme.yml:

extensions:
  .default_file: {icon: {glyph: "f"}}
  .default_file_unknown: {icon: {glyph: "?"}}
  .default_directory: {icon: {glyph: "d"}}
  .default_directory_empty: {icon: {glyph: "e"}}

Using '.' prefix to not conflict with actual file extensions.

Output:

$ eza -ln --icons
drwxr-xr-x - 1000 22 Aug 19:18 d  dir
drwxr-xr-x - 1000 22 Aug 19:17 e  empty-dir
.rw-r--r-- 0 1000 22 Aug 19:17 ?  file
.rw-r--r-- 0 1000 22 Aug 19:18 f  file.randomextension

[sand4rt]

Wouldn’t it make more sense to extend the exsisting properties?:

filekinds:
    normal: {icon: {glyph: "f"}}
    normal_unknown: {icon: {glyph: "?"}} # new property
    directory: {icon: {glyph: "d"}}
    directory_empty: {icon: {glyph: "e"}} #new property

instead of:

extensions:
  .default_file: {icon: {glyph: "f"}}
  .default_file_unknown: {icon: {glyph: "?"}}
  .default_directory: {icon: {glyph: "d"}}
  .default_directory_empty: {icon: {glyph: "e"}}

---

full api:

filekinds:
  normal: { filename: { foreground: White }, icon: { foreground: Blue, glyph: f } }
  normal_unknown: { filename: { foreground: White }, icon: { foreground: Blue, glyph: ? } }
  directory: { filename: { foreground: White }, icon: { foreground: Blue, glyph: d } }
  directory_empty: { filename: { foreground: White }, icon: { foreground: Blue, glyph: e } }

[Flachz]

@sand4rt I agree this would be the best place to put it. The reason I did not was that those are currently seperate code paths that would require (comparatively) a lot of changes to make it work. It would also be a breaking change, as it would change the schema of the theme config in a non backward compatible way.

But having it atleast as its own field should be a lot better already, instead of cramming it in with extensions.

I'll see if I manage to implement this in a better way. At the moment I don't think this PR should be merged in its current state, so I'll mark it as draft for now.

[sand4rt]

It would also be a breaking change, as it would change the schema of the theme config in a non backward compatible way

I dont think this have to be true right? The old syntax is still supported when the type is: normal: {foreground: "#e0def4"} | { filename: { foreground: White }, icon: { foreground: Blue, glyph: f } }