[doc] Remove "Edit me" button for language index pages

[adangel]

Well I was not sure if it would be right to raise as an issue.

Issue

Page opened from "Edit me" does not exists.

Originally posted by @codeanit in #3223

[adangel]

We probably need to add a new property for these pages and use this additional property at

pmd/docs/_layouts/page.html

Lines 42 to 51 in 3989c08

	{% if site.github_editme_path %}
	{% assign editmepath = page.path %}
	{% if page.editmepath %}
	{% assign editmepath = page.editmepath %}
	{% endif %}
	<a target="_blank" href="https://github.com/{{site.github_editme_path}}{{editmepath}}" class="btn btn-default githubEditButton" role="button"><i class="fa fa-github fa-lg"></i> Edit me</a>
	{% endif %}

to decide whether to display the button or not.

Currently, a page can override the "editmepath", but can't disable the button completely.

The property needs to be added when these rule index pages are generated, somewhere here:

pmd/pmd-doc/src/main/java/net/sourceforge/pmd/docs/RuleDocGenerator.java

Lines 178 to 185 in 3989c08

	lines.add("---");
	lines.add("title: " + entry.getKey().getName() + " Rules");
	lines.add("tags: [rule_references, " + languageTersename + "]");
	lines.add("summary: Index of all built-in rules available for " + entry.getKey().getName());
	lines.add("language_name: " + entry.getKey().getName());
	lines.add("permalink: " + LANGUAGE_INDEX_PERMALINK_PATTERN.replace("${language.tersename}", languageTersename));
	lines.add("folder: pmd/rules");
	lines.add("---");