In relation to Bug 1019640 and fixing spelling mistake in webmaker.org.JSON file

In the Webmaker.org footer, in the line of text "with support from our wonderful partners and Mozillians like you!" ––  the word[Mozillians] should link to `https://mozillians.org/en-US/`

Also fixed an additional mistake in the `webmaker.org.json` file and `layout.html` file, regarding the spelling of "Mozillians".