patch 9.1.0506: filetype: .envrc & .prettierignore not recognized

patch 9.1.0506: filetype: .envrc & .prettierignore not recognized

Problem:  filetype: .envrc & .prettierignore not recognized
Solution: Detect '.envrc' as shell and '.prettierignore' as gitignore
          filetype (Tyler Miller)

Support ft detection for `.envrc` files used by direnv, and
`.prettierignore` files used by prettier.

closes: #15053
resolves: neovim/neovim#29405

Signed-off-by: Tyler Miller <tmillr@proton.me>
Signed-off-by: Christian Brabandt <cb@256bit.org>