GHA/checkdocs: re-enable proselint, update setup, fix issues found

- update configuration and invocation.
- install via pip.
- drop a file exception.
- alpha sort proselint settings.
- FILEFORMAT: update text about XML compliance.
- CI job takes 22 seconds total.

Ref: https://github.com/amperser/proselint/releases/tag/v0.16.0

Follow-up to 38bfe1c2aa #15314

Closes #19931

.github/scripts/requirements-proselint.txt

@@ -0,0 +1,5 @@
+# Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
+#
+# SPDX-License-Identifier: curl
+
+proselint==0.16.0

.github/workflows/checkdocs.yml

@@ -35,59 +35,57 @@ concurrency:
 permissions: {}
 
 jobs:
-  #  proselint:
-  #    name: 'proselint'
-  #    runs-on: ubuntu-latest
-  #    steps:
-  #      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5.0.0
-  #        with:
-  #          persist-credentials: false
-  #
-  #      - name: 'install prereqs'
-  #        run: |
-  #          sudo rm -f /etc/apt/sources.list.d/microsoft-prod.list
-  #          sudo apt-get -o Dpkg::Use-Pty=0 update
-  #          sudo rm -f /var/lib/man-db/auto-update
-  #          sudo apt-get -o Dpkg::Use-Pty=0 install python3-proselint
-  #
-  #      # config file help: https://github.com/amperser/proselint/
-  #      - name: 'create proselint config'
-  #        run: |
-  #          cat <<JSON > ~/.proselintrc.json
-  #          {
-  #            "checks": {
-  #              "typography.diacritical_marks": false,
-  #              "typography.symbols": false,
-  #              "annotations.misc": false,
-  #              "security.password": false,
-  #              "misc.annotations": false
-  #            }
-  #          }
-  #          JSON
-  #
-  #      - name: 'trim headers off all *.md files'
-  #        run: git ls-files '*.md' -z | xargs -0 -n1 .github/scripts/trimmarkdownheader.pl
-  #
-  #      - name: 'check prose'
-  #        run: git ls-files '*.md' -z | grep -Evz 'CHECKSRC\.md|DISTROS\.md|curl_mprintf\.md|CURLOPT_INTERFACE\.md|interface\.md' | xargs -0 proselint -- README
-  #
-  #      # This is for CHECKSRC and files with aggressive exclamation mark needs
-  #      - name: 'create second proselint config'
-  #        run: |
-  #          cat <<JSON > ~/.proselintrc.json
-  #          {
-  #            "checks": {
-  #              "typography.diacritical_marks": false,
-  #              "typography.symbols": false,
-  #              "typography.exclamation": false,
-  #              "lexical_illusions.misc": false,
-  #              "annotations.misc": false
-  #            }
-  #          }
-  #          JSON
-  #
-  #      - name: 'check special prose'
-  #        run: proselint docs/internals/CHECKSRC.md docs/libcurl/curl_mprintf.md docs/libcurl/opts/CURLOPT_INTERFACE.md docs/cmdline-opts/interface.md
+  # config file help: https://github.com/amperser/proselint/
+  proselint:
+    name: 'proselint'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
+        with:
+          persist-credentials: false
+
+      - name: 'install prereqs'
+        run: |
+          python3 -m venv ~/venv
+          ~/venv/bin/pip --disable-pip-version-check --no-input --no-cache-dir install --progress-bar off --prefer-binary -r .github/scripts/requirements-proselint.txt
+
+      - name: 'trim headers off all *.md files'
+        run: git ls-files '*.md' -z | xargs -0 -n1 .github/scripts/trimmarkdownheader.pl
+
+      - name: 'check prose'
+        run: |
+          cat <<JSON > ~/.proselintrc.json
+          {
+            "checks": {
+              "annotations.misc": false,
+              "lexical_illusions": false,
+              "misc.annotations": false,
+              "redundancy.misc.garner": false,
+              "security.password": false,
+              "spelling.ve_of": false,
+              "typography.diacritical_marks": false,
+              "typography.symbols": false
+            }
+          }
+          JSON
+          source ~/venv/bin/activate
+          git ls-files README '*.md' -z | grep -Evz '(CHECKSRC|DISTROS|CURLOPT_INTERFACE|interface)\.md' | xargs -0 proselint check --
+
+      - name: 'check special prose'  # For CHECKSRC and files with aggressive exclamation mark needs
+        run: |
+          cat <<JSON > ~/.proselintrc.json
+          {
+            "checks": {
+              "annotations.misc": false,
+              "lexical_illusions": false,
+              "typography.diacritical_marks": false,
+              "typography.punctuation.exclamation": false,
+              "typography.symbols": false
+            }
+          }
+          JSON
+          source ~/venv/bin/activate
+          proselint check docs/internals/CHECKSRC.md docs/libcurl/opts/CURLOPT_INTERFACE.md docs/cmdline-opts/interface.md
 
   pyspelling:
     name: 'pyspelling'