About those Invisible files in your Drupal installation

.editorconfig

“…so you can enjoy a consistent coding style between different editors and IDEs. No need to configure anymore the editor for every project.”

This file allows you to set certain default behaviors for consistent use in your site's text editors.

An example of an .editorconfig file:

# Drupal editor configuration normalization
# @see http://editorconfig.org/

# This is the top-most .editorconfig file; do not search in parent directories.
root = true

# All files.
[*]
end_of_line = LF
indent_style = space
indent_size = 2
charset = utf-8
trim_trailing_whitespace = true
insert_final_newline = true

[composer.{json,lock}]
indent_size = 4

.gitattributes

A gitattributes file is a simple text file that gives attributes to pathnames.
Each line in gitattributes file is of form:

Similar to the .editorconfig file, this file provides for consistent formatting between files for developers editing with git. One example is with the end-of-line character that is used.

*.js    eol=lf
*.txt   eol=lf
*.json  eol=lf

.csslintrc

CSS Lint is a tool to help point out problems with your CSS code. It does basic syntax checking as well as applying a set of rules to the code that look for problematic patterns or signs of inefficiency. The rules are all pluggable, so you can easily write your own or omit ones you don’t want.

{
	"adjoining-classes": false,
	"box-model": false,
	"box-sizing": false,
	"bulletproof-font-face": false,
	"compatible-vendor-prefixes": false,
	"display-property-grouping": false,
	"duplicate-background-images": false,
	"duplicate-properties": false,
	"empty-rules": false,
	"errors": false,
	"fallback-colors": false,
	"floats": false,
	"font-faces": false,
	"font-sizes": false,
	"gradients": false,
	"ids": false,
	"import": false,
	"import-ie-limit": false,
	"important": false,
	"known-properties": false,
	"non-link-hover": false,
	"order-alphabetical": false,
	"outline-none": false,
	"overqualified-elements": false,
	"qualified-headings": false,
	"regex-selectors": false,
	"rules-count": false,
	"selector-max": false,
	"selector-max-approaching": false,
	"selector-newline": false,
	"shorthand": false,
	"star-property-hack": false,
	"text-indent": false,
	"underscore-property-hack": false,
	"unique-headings": false,
	"universal-selector": false,
	"unqualified-attributes": false,
	"vendor-prefix": false,
	"zero-units": false
}

.htrouter.php

This is used with php internal web server so it might not come in handy if your are using apache.

“…the htrouter.php file for use with the built in php server and the Phlacon PHP framework.”

.eslintignore

You can tell ESLint to ignore specific files and directories using ignorePatterns in your config files. ignorePatterns patterns follow the same rules as .eslintignore. Please see the the .eslintignore file documentation to learn more.

.gitignore

.eslinre.json