Add a 'theme' for OMP, so the internal themes don't clash with it.

themes/oh-my-posh/oh-my-posh.theme.bash

@@ -0,0 +1,20 @@
+# shellcheck shell=bash
+
+if _command_exists oh-my-posh; then
+	export POSH_THEME=${POSH_THEME:-https://raw.githubusercontent.com/JanDeDobbeleer/oh-my-posh/v$(oh-my-posh --version)/themes/jandedobbeleer.omp.json}
+	eval "$(oh-my-posh --init --shell bash --config "${POSH_THEME}")"
+else
+	_log_warning "The oh-my-posh binary was not found on your \$PATH."
+	_log_warning "Falling back to your existing \$PS1."
+	_log_warning
+	_log_warning "*** Note:"
+	_log_warning "The oh-my-posh ״theme״ is really a plug to a whole other system"
+	_log_warning "of managing your prompt. To use it please start here:"
+	_log_warning "https://ohmyposh.dev/"
+	_log_warning
+	_log_warning "It is beyond the scope of bash-it to install and manage oh-my-posh,"
+	_log_warning "this theme is here just to make sure your OMP setup doesn't clash"
+	_log_warning "with other bash-it themes. Once installed, OMP will load a default"
+	_log_warning "OMP theme (powerlevel10k_rainbow), which you can then"
+	_log_warning "customize or override."
+fi