Add developer support files

.editorconfig

+# 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

+# Drupal git normalization
+# @see https://www.kernel.org/pub/software/scm/git/docs/gitattributes.html
+# @see https://www.drupal.org/node/1542048
+
+# Normally these settings would be done with macro attributes for improved
+# readability and easier maintenance. However macros can only be defined at the
+# repository root directory. Drupal avoids making any assumptions about where it
+# is installed.
+
+# Define text file attributes.
+# - Treat them as text.
+# - Ensure no CRLF line-endings, neither on checkout nor on checkin.
+# - Detect whitespace errors.
+#   - Exposed by default in `git diff --color` on the CLI.
+#   - Validate with `git diff --check`.
+#   - Deny applying with `git apply --whitespace=error-all`.
+#   - Fix automatically with `git apply --whitespace=fix`.
+
+*.config  text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.css     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.dist    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.engine  text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.html    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=html
+*.inc     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.install text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.js      text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.json    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.lock    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.map     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.md      text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.module  text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.php     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.po      text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.profile text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.script  text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.sh      text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.sql     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.svg     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.theme   text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2 diff=php
+*.twig    text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.txt     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.xml     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+*.yml     text eol=lf whitespace=blank-at-eol,-blank-at-eof,-space-before-tab,tab-in-indent,tabwidth=2
+
+# Define binary file attributes.
+# - Do not treat them as text.
+# - Include binary diff in patches instead of "binary files differ."
+*.eot     -text diff
+*.exe     -text diff
+*.gif     -text diff
+*.gz      -text diff
+*.ico     -text diff
+*.jpeg    -text diff
+*.jpg     -text diff
+*.otf     -text diff
+*.phar    -text diff
+*.png     -text diff
+*.svgz    -text diff
+*.ttf     -text diff
+*.woff    -text diff
+*.woff2   -text diff

.gitignore

+# IDE/sysem paths.
+.idea
+
+# Vendor paths.
+composer.lock
+vendor
\ No newline at end of file

.phpcs.xml.dist

+<ruleset name="drupal/jsonapi_image_styles">
+    <description>JSON:API Image Styles module CodeSniffer configuration.</description>
+
+    <arg name="extensions" value="php,module,inc,install,test,profile,theme,css,info,md,yml"/>
+    <config name="drupal_core_version" value="9"/>
+
+    <file>.</file>
+    <exclude-pattern>vendor</exclude-pattern>
+
+    <rule ref="./vendor/drupal/coder/coder_sniffer/Drupal"/>
+    <rule ref="./vendor/drupal/coder/coder_sniffer/DrupalPractice"/>
+</ruleset>