[ALOY-1522] Silence Alloy warnings about non-model files for file names that begin with a period

During our build process, we're getting a warning from Alloy: {noformat} Non-model file ".eslintrc.json" in models directory {noformat} We are using eslint in our project and need to specify some special settings for the model files. I see in the Alloy source code (commands/compile/index.js:934) that this warning is displayed for each file that doesn't match the RegEx (basically any file that doesn't end in "js"). I could avoid the warning by making it an .eslint.js file, but that would mean it would get copied to the final product (which I'd like to avoid). It seems like it would be a nice addition if files that start with a period are skipped and don't produce warnings.