Update readme

Author: guustysebie

BUILDING.md

@@ -14,5 +14,5 @@ environment variables. Examples of paths on Windows:
 If you have a new version of ImageMagick, then there is no compare.exe utility there, wrap the path to magick.exe in quotes and call compare command:
 ITEXT_MAGICK_COMPARE_EXEC=`"C:\Program Files\ImageMagick-7.0.9-Q16\magick.exe" compare`
 
-[1]: http://www.ghostscript.com/
-[2]: http://www.imagemagick.org/
+[1]: https://www.ghostscript.com/
+[2]: https://www.imagemagick.org/

CODE_OF_CONDUCT.md

@@ -55,7 +55,7 @@ further defined and clarified by project maintainers.
 ## Enforcement
 
 Instances of abusive, harassing, or otherwise unacceptable behavior may be
-reported by contacting the project team at http://itextpdf.com/contact. All
+reported by contacting the project team at https://itextpdf.com/contact. All
 complaints will be reviewed and investigated and will result in a response that
 is deemed necessary and appropriate to the circumstances. The project team is
 obligated to maintain confidentiality with regard to the reporter of an incident.
@@ -68,7 +68,7 @@ members of the project's leadership.
 ## Attribution
 
 This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
-available at [http://contributor-covenant.org/version/1/4][version]
+available at [https://contributor-covenant.org/version/1/4][version]
 
-[homepage]: http://contributor-covenant.org
-[version]: http://contributor-covenant.org/version/1/4/
+[homepage]: https://contributor-covenant.org
+[version]: https://contributor-covenant.org/version/1/4/

CONTRIBUTING.md

@@ -159,7 +159,7 @@ Please note that this project is released with a [Contributor Code of Conduct][c
 
 We use the [Stack Exchange][stackoverflow] network for free support and [GitHub][github] for code hosting. By using these services, you agree to abide by their terms:
 
-* StackExchange: [http://stackexchange.com/legal](http://stackexchange.com/legal)
+* StackExchange: [https://stackexchange.com/legal](https://stackexchange.com/legal)
 * Github: [https://help.github.com/articles/github-terms-of-service/](https://help.github.com/articles/github-terms-of-service/)
 
 [cla]: https://itextpdf.com/en/how-buy/legal/itext-contributor-license-agreement
@@ -168,7 +168,7 @@ We use the [Stack Exchange][stackoverflow] network for free support and [GitHub]
 [java-style-guide]: https://www.oracle.com/technetwork/java/codeconvtoc-136057.html
 [javadocs]: https://itextpdf.com/api
 [pull]: https://github.com/itext/itext7-dotnet/pulls
-[sscce]: http://sscce.org/
+[sscce]: https://sscce.org/
 [stackoverflow]: https://stackoverflow.com/questions/tagged/itext
 [good-questions]: https://stackoverflow.com/help/how-to-ask
 [mcve]: https://stackoverflow.com/help/mcve
@@ -180,4 +180,4 @@ We use the [Stack Exchange][stackoverflow] network for free support and [GitHub]
 [git-commit-end]: https://chris.beams.io/posts/git-commit/#end
 [git-commit-imperative]: https://chris.beams.io/posts/git-commit/#imperative
 [git-commit-wrap-72]: https://chris.beams.io/posts/git-commit/#wrap-72
-[git-commit-why-not-how]: https://chris.beams.io/posts/git-commit/#why-not-how
+[git-commit-why-not-how]: https://chris.beams.io/posts/git-commit/#why-not-how