Fix character literal not storing its contents

[ire4ever1190]

The character literal was only storing its contents in a node when it was an escape sequence. Was writing a formatter with topiary but was running into issues with characters since their contents would get lost e.g.

discard '?'
discard '\n'
discard "hello"

[2026-01-01T00:52:38Z ERROR topiary::error] Cause:   × Parsing error between line 0, column 0 and line 0, column 10
       ╭─[standard input:1:1]
     1 │ discard ''
       · ─────┬─────
       ·      ╰── (ERROR) node
     2 │ discard '\n'
     3 │ discard "hello"
       ╰────

[alaviss]

LGTM, thanks for contributing!