Modernize CI (onboard to plone/meta) (#1883)

* Configuring with plone.meta

* plone.meta tweaks, convert to markdown

* Configuring with plone.meta

* Update CI & Makefile

* cleanup

* Try to fix uncommitted docs check

* fix rtd

* Fix make test dependencies

* Update examples

* disable dependencies check

* build mo files for tests

* Don't drop old Pythons just yet

* lint

* Fix plone.rest version for 5.2

* Fix compiling mo files for test

* Update i18n script

* nitpick

Author: davisagli

.editorconfig

@@ -1,4 +1,58 @@
+# Generated from:
+# https://github.com/plone/meta/tree/main/src/plone/meta/default
+# See the inline comments on how to expand/tweak this configuration file
+#
+# EditorConfig Configuration file, for more details see:
+# http://EditorConfig.org
+# EditorConfig is a convention description, that could be interpreted
+# by multiple editors to enforce common coding conventions for specific
+# file types
+
+# top-most EditorConfig file:
+# Will ignore other EditorConfig files in Home directory or upper tree level.
 root = true
 
+
+[*]
+# Default settings for all files.
+# Unix-style newlines with a newline ending every file
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+# Set default charset
+charset = utf-8
+# Indent style default
+indent_style = space
+# Max Line Length - a hard line wrap, should be disabled
+max_line_length = off
+
+[*.{py,cfg,ini}]
+# 4 space indentation
+indent_size = 4
+
+[*.{yml,zpt,pt,dtml,zcml,html,xml}]
+# 2 space indentation
+indent_size = 2
+
+[*.{json,jsonl,js,jsx,ts,tsx,css,less,scss}]
+# Frontend development
+# 2 space indentation
+indent_size = 2
+max_line_length = 80
+
+[{Makefile,.gitmodules}]
+# Tab indentation (no size specified, but view as 4 spaces)
+indent_style = tab
+indent_size = unset
+tab_width = unset
+
 [*.resp]
 trim_trailing_whitespace = false
+
+##
+# Add extra configuration options in .meta.toml:
+#  [editorconfig]
+#  extra_lines = """
+#  _your own configuration lines_
+#  """
+##

.flake8

@@ -1,9 +1,24 @@
+# Generated from:
+# https://github.com/plone/meta/tree/main/src/plone/meta/default
+# See the inline comments on how to expand/tweak this configuration file
 [flake8]
-# Recommend matching the black line length (default 88),
-# rather than using the flake8 default of 79:
-max-line-length = 100000
-extend-ignore =
-    # See https://github.com/PyCQA/pycodestyle/issues/373
+doctests = 1
+ignore =
+    # black takes care of line length
+    E501,
+    # black takes care of where to break lines
+    W503,
+    # black takes care of spaces within slicing (list[:])
     E203,
+    # black takes care of spaces after commas
+    E231,
 per-file-ignores =
     src/plone/restapi/bbb.py:F401
+
+##
+# Add extra configuration options in .meta.toml:
+#  [flake8]
+#  extra_lines = """
+#  _your own configuration lines_
+#  """
+##