Nim lang support (#979)

<!--- PR Description --->
Closes #978
---
#### TODO

- [x] Use `cargo fmt`
- [ ] Add necessary tests
- [ ] Update default config/theme in README (if applicable)
- [ ] Update man page at lsd/doc/lsd.md (if applicable)

src/theme/icon.rs

@@ -580,6 +580,8 @@ impl IconTheme {
             ("msi", "\u{f17a}"),             // ""
             ("mts", "\u{e628}"),             // ""
             ("mustache", "\u{e60f}"),        // ""
+            ("nim", "\u{e677}"),             // ""
+            ("nimble", "\u{e677}"),          // ""
             ("nix", "\u{f313}"),             // ""
             ("npmignore", "\u{e71e}"),       // ""
             ("odp", "\u{f1c4}"),             // ""