modernize and cleanup documentation (#542)

* disable system packages on rtd

* install pycups on rtd

* enable cups binding in documentation

* document CupsPrinter

* fix formatting

* revise methods and installation

* revise user/printers

* revise raspi section

* further revise

doc/printer_profiles/available-encodings.rst

@@ -1,6 +1,11 @@
 Available Encodings
 -------------------
-:Last Reviewed: 2023-07-29
+:Last Reviewed: 2023-08-10
+
+If you find any issues with the described encodings,
+please open an issue in the
+`ESC/POS printer database <https://github.com/receipt-print-hq/escpos-printer-db>`_.
+The data shown here is directly taken from there.
 
 .. datatemplate:json:: ../../capabilities-data/dist/capabilities.json
    :template: capabilities-template-encoding.jinja

doc/printer_profiles/available-profiles.rst

@@ -2,7 +2,7 @@
 
 Available Profiles
 ------------------
-:Last Reviewed: 2023-07-29
+:Last Reviewed: 2023-08-10
 
 The following list describes which printer profiles are
 available in this release.
@@ -12,6 +12,7 @@ that this printer actually can be controlled by this library.
 If you find any issues with the described capabilities,
 please open an issue in the
 `ESC/POS printer database <https://github.com/receipt-print-hq/escpos-printer-db>`_.
+The data shown here is directly taken from there.
 
 .. datatemplate:json:: ../../capabilities-data/dist/capabilities.json
    :template: capabilities-template.jinja

doc/printer_profiles/capabilities.rst

@@ -2,7 +2,7 @@
 
 Capabilities
 ------------
-:Last Reviewed: 2023-07-29
+:Last Reviewed: 2023-08-10
 
 Since the used command set often differs between printers,
 a model for supporting different printers is implemented.