Fix some markdownlint warnings on .md files

[gian1200]

Closes #40147

Fixed some non intrusive warnings: in some .md files

• MD009: Remove extra trailing spaces
• MD031: Add new line
• MD034: Add wrappers to URL (<>)
• MD038: Remove extra spaces from code span element
• MD040: Specify language on code block
• MD051: Fix Link fragments in CONTRIBUTING.md index (rolled back)

PS:

• markdown-toc has a bug where generates bad links when special characters are used in headings
• CONTRIBUTING.md still has 192 warnings that should be reviewed:
  • MD001/heading-increment: Heading levels should only increment by one level at a time [Expected: h3; Actual: h4]
  • MD004/ul-style: Unordered list style [Expected: dash; Actual: asterisk]
  • MD007/ul-indent: Unordered list indentation [Expected: 2; Actual: 4]
  • MD033/no-inline-html: Inline HTML [Element: a]
  • MD036/no-emphasis-as-heading: Emphasis used instead of a heading
  • MD040/fenced-code-language: Fenced code blocks should have a language specified
  • MD049/emphasis-style: Emphasis style [Expected: asterisk; Actual: underscore]

[gsmet]

Thanks for taking the time to prepare this PR.

All changes look good except the change to the TOC: given it's automatically generated, I don't think we want to adjust it.

[quarkus-bot]

Status for workflow Quarkus CI

This is the status report for running Quarkus CI on commit 840c1f3.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

You can consult the Develocity build scans.

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Flaky tests - Develocity

⚙️ JVM Tests - JDK 17

📦 integration-tests/rest-client

✖ io.quarkus.it.rest.client.wronghost.ExternalWrongHostUsingVerifyHostTestCase.restClient - History

• Read timed out - java.net.SocketTimeoutException

java.net.SocketTimeoutException: Read timed out
	at java.base/sun.nio.ch.NioSocketImpl.timedRead(NioSocketImpl.java:288)
	at java.base/sun.nio.ch.NioSocketImpl.implRead(NioSocketImpl.java:314)
	at java.base/sun.nio.ch.NioSocketImpl.read(NioSocketImpl.java:355)
	at java.base/sun.nio.ch.NioSocketImpl$1.read(NioSocketImpl.java:808)
	at java.base/java.net.Socket$SocketInputStream.read(Socket.java:966)
	at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:161)
	at org.apache.http.impl.io.SocketInputBuffer.fillBuffer(SocketInputBuffer.java:82)