feat(lint): add rules for lowercase file names, max line length and no tab indentation

src/rules/lowerCaseFileNames.spec.ts

@@ -0,0 +1,27 @@
+import { Severity } from '../types/Severity'
+import { lowerCaseFileNames } from './lowerCaseFileNames'
+
+describe('lowerCaseFileNames', () => {
+  it('should return an empty array when the file name has no uppercase characters', () => {
+    const filePath = '/code/sas/my_sas_file.sas'
+    expect(lowerCaseFileNames.test(filePath)).toEqual([])
+  })
+
+  it('should return an empty array when the file name has no uppercase characters, even if the containing folder has uppercase characters', () => {
+    const filePath = '/code/SAS Projects/my_sas_file.sas'
+    expect(lowerCaseFileNames.test(filePath)).toEqual([])
+  })
+
+  it('should return an array with a single diagnostic when the file name has uppercase characters', () => {
+    const filePath = '/code/sas/my SAS file.sas'
+    expect(lowerCaseFileNames.test(filePath)).toEqual([
+      {
+        message: 'File name contains uppercase characters',
+        lineNumber: 1,
+        startColumnNumber: 1,
+        endColumnNumber: 1,
+        severity: Severity.Warning
+      }
+    ])
+  })
+})