[docs]: Fix markdownlint warnings for standard formatting of Markdown docs

[bernhardkaindl]

Summary

Improve the legibility of the Markdown documentation files for xen-bugtool by addressing the markdownlint warnings.

git diff HEAD~~~~ | diffstat
 .markdownlint.yaml            |   47 +++++++++++++++++++++++++++
 .pre-commit-config.yaml       |   10 +++++
 README-Windows-WSL2.md        |    2 -
 README-python-install.md      |    6 ++-
 README.md                     |   21 ++++++++++--
 doc/coverage.md               |    2 -
 doc/pre-commit.md             |   36 ++++++++++++++-------
 doc/release.md                |   16 +++++++--
 doc/testing.md                |   25 +++++++-------
 tests/unit/conftest-README.md |   81 +++++++++++++++++++++++++++---------------------
 10 files changed, 177 insertions(+), 69 deletions(-)

Added configuration to check Markdown files using markdownlint

• .markdownlint.yaml: Add a markdownlint configuration file to tune specific linting rules
• .pre-commit-config.yaml: Support running markdownlint using pre-commit run -a markdownlint, requires a relatively modern Linux host (> Ubuntu 22.04).

Example on a fresh install of Debian 12:

$ sudo apt install pipx
$ pipx install pre-commit
$ pipx ensurepath
$ bash
$ pre-commit run -a markdownlint
[...]
[INFO] Installing environment for https://github.com/igorshubovych/markdownlint-cli.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
markdownlint.............................................................Passed

[Copilot]

Pull Request Overview

This PR fixes markdownlint warnings across documentation files and establishes markdownlint as a pre-commit hook to maintain consistent markdown formatting. It also adds comprehensive documentation for xen-bugtool's plugin system.

• Fix markdownlint formatting issues across multiple documentation files
• Add markdownlint configuration and pre-commit hook for automated checking
• Create detailed plugin documentation explaining XML structure and workflow

Reviewed Changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/unit/conftest-README.md	Fix markdown formatting issues and improve documentation structure
doc/testing.md	Fix header formatting and typos, improve list structure
doc/release.md	Add missing blank lines around code blocks and improve formatting
doc/pre-commit.md	Fix header levels, improve link formatting, and fix typos
doc/plugins.md	New documentation explaining xen-bugtool plugin XML structure and workflow
doc/coverage.md	Fix header level from ## to #
README.md	Improve organization and add missing blank lines
README-python-install.md	Fix header level and spelling error
README-Windows-WSL2.md	Fix header level formatting
.pre-commit-config.yaml	Add markdownlint hook configuration
.markdownlint.yaml	Add markdownlint configuration with project-specific rules

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[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated no new comments.

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[bernhardkaindl]

• Rebased on top of the latest merge to master to resolve a small conflict.
• Applied fixes after review using Sourcery's review robot.

[bernhardkaindl]

• Rebased again on top of today's merge to be on top of today's new master.
• Applied fixes after review using Sourcery's review robot.
• Formatted long lines and shortened the maximum line lengths.

[bernhardkaindl]

Added Cleanup outdated radon code complexity result output as it overlaps with the markdownlint fixes.

[bernhardkaindl]

I've:

• Split the fixes for tests/unit/conftest-README.md into #169 as it allows for better review
• Suashed the cleanup of the no longer relevant table on the cyclomatic complexity of other XS Python projects or scripts into the README.md changes
• Rebased on the current master.