Add erdtree install and config

erdtree/.config/erdtree/config

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+--icons

erdtree/.config/profile/env.d/erdtree.env

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+ERDTREE_CONFIG_PATH=${XDG_CONFIG_HOME}/erdtree/config

erdtree/.local/bin/install-erdtree

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+#!/usr/bin/env bash
+
+source "${XDG_DATA_HOME}/buddy-up/includes/utils.sh"
+
+
+function get_os () (
+    case $(uname -s) in
+        Linux*)     echo unknown-linux-gnu;;
+        Darwin*)    echo apple-darwin;;
+        *)          >&2 echo "unsupported os: $(uname -s)"; exit 1;;
+    esac
+)
+
+function get_arch () (
+    uname -m
+)
+
+APP=erdtree
+VERSION=${VERSION:-1.4.1}
+DEST="${XDG_DATA_HOME}/apps/releases/${APP}"
+URL=https://github.com/solidiquis/erdtree/releases/download/v${VERSION}/et-v${VERSION}-$(get_arch)-$(get_os).tar.gz
+
+extract_tarball "${URL}" "${DEST}/${VERSION}"
+set_current_link "${DEST}" "${VERSION}"
+set_link "${XDG_BIN_HOME}/et" "${DEST}" "et"