[openssl/openssl] 9e87e4: Update .gitignore with LSP files

[Todd Short]

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 9e87e4e8ac2c5c75eae0ef1d4208e2aa12ff57dc
      https://github.com/openssl/openssl/commit/9e87e4e8ac2c5c75eae0ef1d4208e2aa12ff57dc
  Author: Todd Short <todd.short at me.com>
  Date:   2023-07-02 (Sun, 02 Jul 2023)

  Changed paths:
    M .gitignore

  Log Message:
  -----------
  Update .gitignore with LSP files

This does not provide files for LSP support, but ignores them so they
aren't accidentally checked in by developers.

LSP (Language Server Protocol) is a tools that can be used with various
editors to make navigating source code easier. It is more advanced than
`cscope` and supports completion, for example.

A common LSP for C/C++ is `clangd`, and it creates a `.cache` directory
within the project to store data.

The tool `bear` can be used with `make` to assist `clangd` in
determining where the source code is (specifically headers). This is
critical as OpenSSL uses the `<>` form of `#include` rather than the
`""` form. The `<>` form will cause `clangd` to look in e.g.
`/usr/include` for header files, rather than `include/openssl`. The
`bear` tool will create `compile_commands.json` that `clangd` can use
to find include files.

Reviewed-by: Shane Lontis <shane.lontis at oracle.com>
Reviewed-by: Paul Dale <pauli at openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21338)