Simplify package bootstrapping

* Install always the newest packages from the archives.
* Stop using ~quelpa~, but keep it for future use.
* Use ~package-install~ to install ~eglot~.
* Add ~markdown-mode~ and ~rainbow-mode~.

README.org

@@ -170,8 +170,6 @@ in the ~custom-set-variable~ function call below.
    `(insert-directory-program ,(or (executable-find "gls")
                                    (executable-find "ls")))
    '(kill-ring-max 300)
-   '(package-archive-priorities '(("gnu" . 1)
-                                  ("nongnu" . 1)))
    '(package-archives '(("gnu" . "https://elpa.gnu.org/packages/")
                         ("nongnu" . "https://elpa.nongnu.org/nongnu/")
                         ("melpa" . "https://melpa.org/packages/")))
@@ -215,13 +213,13 @@ in the ~custom-set-variable~ function call below.
 :CUSTOM_ID: sec:package-bootstrapping
 :END:
 
-[[info:emacs#Package Installation][Emacs installs packages]] from archives on the internet.
-This setup uses three  archives in two decreasing levels of priority:
-1. The [[https://elpa.gnu.org/][GNU Emacs Lisp Package Archive]] or the [[https://elpa.nongnu.org/][NonGNU Emacs Lisp Package Archive]].
+[[info:emacs#Package Installation][Emacs installs packages]] from archives on the internet.  This setup uses three
+archives:
+1. The [[https://elpa.gnu.org/][GNU Emacs Lisp Package Archive]]
+2. The [[https://elpa.nongnu.org/][NonGNU Emacs Lisp Package Archive]].
 3. The [[https://melpa.org/#/][MELPA - Milkypostman’s Emacs Lisp Package Archive]].
 Finally, the [[https://github.com/quelpa/quelpa][quelpa]] tool allows to fetch code from any source and build a
-package on your computer before installation. It allows to install a package
-from [[https://melpa.org/#/][MELPA]] instead of [[https://elpa.gnu.org/][GNU ELPA]] or [[https://elpa.nongnu.org/][NonGNU ELPA]], breaking the priority order.
+package on your computer before installation.
 
 The output of the byte-compiler may change with each new Emacs release.
 Therefore, in order to prevent collisions between different Emacs versions, the
@@ -241,8 +239,8 @@ any packages, hence also [[https://github.com/emacscollective/no-littering][no-l
 You have to refresh the list of available packages yourself before updating
 the installed packages.
 
-Finally, ~my-install-packages~ ensures installation of all packages in a list of
-packages.
+Finally, ~my-install-packages~ facilitates installation of all packages in a
+list of packages.
 
 #+attr_latex: :options bgcolor=LightGoldenrodYellow
 #+begin_src emacs-lisp
@@ -280,6 +278,7 @@ compatibility with Emacs-28.1.  The [[info:elisp#Backquote][info:backquote]] pag
       citeproc                    ; bibliography handling
       company-anaconda            ; complete anything in anaconda-mode
       consult                     ; consult completing-read
+      eglot                       ; Emacs polyGLOT LSP client
       embark                      ; act on any buffer selection
       htmlize                     ; convert buffer contents to HTML
       leuven-theme                ; beautiful color theme
@@ -294,26 +293,11 @@ compatibility with Emacs-28.1.  The [[info:elisp#Backquote][info:backquote]] pag
   (my-install-packages my-packages)
 #+end_src
 
-Install ~eglot~ with [[https://github.com/quelpa/quelpa][quelpa]] to get the latest version from [[https://melpa.org/#/][MELPA]].
+Facilitate installlation of the optional packages.
 
 #+attr_latex: :options bgcolor=LightGoldenrodYellow
 #+begin_src emacs-lisp
-  ;; This is the 3rd package bootstrapping block.
-  (when (package-installed-p 'quelpa)
-    (defun my-install-sources (sources)
-      (mapc (lambda (source)
-              (unless (package-installed-p (car source))
-                (quelpa source)))
-            sources))
-    (my-install-sources
-     '((eglot :fetcher github :repo "joaotavora/eglot"))))
-#+end_src
-
-Install the optional packages.
-
-#+attr_latex: :options bgcolor=LightGoldenrodYellow
-#+begin_src emacs-lisp
-  ;; The is the 4th package bootstrapping block.
+  ;; The is the 3rd package bootstrapping block.
   (defvar my-optional-packages
     `(
       ,@(when (version< emacs-version "28.0")
@@ -326,7 +310,9 @@ Install the optional packages.
       iedit                       ; simultaneous multi-entity editing
       laas                        ; LaTeX Auto-Activating Snippets
       magit                       ; Git Text-based User Interface
+      markdown-mode               ; markdown text mode
       nov                         ; EPUB reader
+      rainbow-mode                ; set background color to color string
       smartparens                 ; smart editing of character pairs
       toml-mode                   ; Tom's Obvious Minimal Language mode
       wgrep                       ; open a writable grep buffer