Recreate `electric-newline-and-maybe-indent`

[bearylabs]

Recreate the Emacs electric-newline-and-maybe-indent feature:

• Insert a newline and, if auto-indent is off, also indent based on filetype/language.
• Keybindings (VSCode/Vim equivalents):
  • <Shift+Enter>
  • <Ctrl+j>

Doom Help:

electric-newline-and-maybe-indent is an interactive and natively
compiled function defined in electric.el.gz.

Signature
(electric-newline-and-maybe-indent)

Documentation
Insert a newline.

If electric-indent-mode is enabled, that's that, but if it
is disabled then additionally indent according to major mode.
Indentation is done using the value of indent-line-function.
In programming language modes, this is the same as TAB.
In some text modes, where TAB inserts a tab, this command indents to the
column specified by the function current-left-margin.

Key Bindings
evil-insert-state-map S-
evil-insert-state-map S-RET
global-map C-j
help-quick-use-map C-j

Demos
[Add]

References
electric-newline-and-maybe-indent is unused in electric.el.gz.