Make rule level name text all caps

[per1234]

The rule level (e.g., error, warning) is an important component of the output because it provides the significance of the rule result. The previous all lower case text of the rule level names in the output made it not very visually prominent.

---

Before:

Linting sketch in C:\Users\per\go\src\github.com\arduino\arduino-lint\test\testdata\compliance\Permissive
Rule SS001 result: fail
error: Sketch file/folder name mismatch. The primary sketch file name must match the folder: Permissive.ino. See: https://arduino.github.io/arduino-cli/latest/sketch-specification/#primary-sketch-file
Rule SD001 result: fail
warning: No readme found. Please document your sketch. See: https://docs.github.com/en/free-pro-team@latest/github/creating-cloning-and-archiving-repositories/about-readmes

Finished linting project. Results:
Warning count: 1
Error count: 1
Rules passed: false

After:

Linting sketch in C:\Users\per\go\src\github.com\arduino\arduino-lint\test\testdata\compliance\Permissive
Rule SS001 result: fail
ERROR: Sketch file/folder name mismatch. The primary sketch file name must match the folder: Permissive.ino. See: https://arduino.github.io/arduino-cli/latest/sketch-specification/#primary-sketch-file
Rule SD001 result: fail
WARNING: No readme found. Please document your sketch. See: https://docs.github.com/en/free-pro-team@latest/github/creating-cloning-and-archiving-repositories/about-readmes

Finished linting project. Results:
Warning count: 1
Error count: 1
Rules passed: false

[ubidefeo]

LGTM