refactor: Revert declaration file organization to Target/ directory

This commit reverts the previous file reorganization and moves all TypeScript declaration files (.d.ts) back from the Target/Source/ subdirectories to the Target/ subdirectories.

The change affects:
- Class declarations (Build.d.ts)
- Function declarations (Build, Echo, Entry, Exclude, Exec, File, JSON, Merge, Regex)
- Interface declarations (Build, Build/Set, Echo, Exec, File, JSON)
- Type declarations (Level.d.ts)
- Variable declarations (ESBuild, Level)

Additionally, tsconfig.json is updated to:
- Add "rootDir": "./Source" to explicitly set the source root directory
- Alphabetically reorder the "ignoreDeprecations" option within compilerOptions

This reverts the organization change from the previous commit, reverting to the simpler Target/ directory structure.

Author: NikolaRHristov