Update links, README, contributing, etc.

Marlin/src/HAL/shared/backtrace/unwarmbytab.cpp

@@ -4,7 +4,7 @@
  *
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
  *
  * This library was modified, some bugs fixed, stack address validated
  * and adapted to be used in Marlin 3D printer firmware as backtracer