Added command: getex

[SomajitDey]

Added the command getex along with the necessary test file.

bun test getex gives:

bun test v1.1.38 (bf2f153f)

pkg/commands/getex.test.ts:
✓ without options > gets value [1031.03ms]
✓ ex > gets value and sets expiry in seconds [2847.04ms]
✓ px > gets value and sets expiry in milliseconds [2848.68ms]
✓ exat > gets value and sets expiry in Unix time (seconds) [3841.88ms]
✓ pxat > gets value and sets expiry in Unix time (milliseconds) [3829.22ms]
✓ persist > gets value and removes expiry [2825.41ms]

 6 pass
 0 fail
 17 expect() calls
Ran 6 tests across 1 files. [17.51s]

The following tests also passed:
bun test redis_getex
bun test pipeline

[CahidArda]

Thanks for the contribution!