chore(release): 2.10.4

[cport1]

Security release for #85 (#111). It also ships #110, #82 and #91.

• Bumps webdecoy.php (header and WEBDECOY_VERSION), readme.txt Stable tag, and cdn-files/plugin-info.json.
• Adds changelog entries in changelog.txt, readme.txt and plugin-info.json.
• Adds a readme Upgrade Notice recommending the upgrade.
• Makes the plugin-info description say WAF pushes happen from the dashboard, matching the readme change in fix: the last four places we still promise things we do not do #82.