Avoid changing line endings of png and mmdb files

[wilkinsona]

Without this change, git status shows unexpected changes:

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
	modified:   spring-session-samples/spring-session-sample-boot-findbyusername/src/main/resources/GeoLite2-City.mmdb
	modified:   spring-session-samples/spring-session-sample-boot-findbyusername/src/main/resources/static/images/logo.png
	modified:   spring-session-samples/spring-session-sample-boot-hazelcast/src/main/resources/static/images/logo.png
	modified:   spring-session-samples/spring-session-sample-boot-jdbc/src/main/resources/static/images/logo.png
	modified:   spring-session-samples/spring-session-sample-boot-mongodb-traditional/src/main/resources/static/resources/img/logo.png
	modified:   spring-session-samples/spring-session-sample-boot-redis-json/src/main/resources/static/images/logo.png
	modified:   spring-session-samples/spring-session-sample-boot-redis/src/main/resources/static/images/logo.png
	modified:   spring-session-samples/spring-session-sample-boot-websocket/src/main/resources/static/images/logo.png

git diff revealed that it was related to line endings:

$ git diff

warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-findbyusername/src/main/resources/GeoLite2-City.mmdb.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-findbyusername/src/main/resources/static/images/logo.png.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-hazelcast/src/main/resources/static/images/logo.png.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-jdbc/src/main/resources/static/images/logo.png.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-mongodb-traditional/src/main/resources/static/resources/img/logo.png.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-redis-json/src/main/resources/static/images/logo.png.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-redis/src/main/resources/static/images/logo.png.
The file will have its original line endings in your working directory
warning: CRLF will be replaced by LF in spring-session-samples/spring-session-sample-boot-websocket/src/main/resources/static/images/logo.png.
The file will have its original line endings in your working directory