chore: mandate .js extensions for imports

[danisharora099]

Problem

The codebase currently uses .js extensions on all imports. This is not caught by the compiler/eslint, and these non-.js extensions can leak in.

Solution

Add an eslint check to catch non .js imports

[github-actions]

size-limit report 📦

Path	Size	Loading time (3g)	Running time (snapdragon)	Total time
Waku node	82.97 KB (0%)	1.7 s (0%)	2.8 s (+45.83% 🔺)	4.5 s
Waku Simple Light Node	134.85 KB (0%)	2.7 s (0%)	2.9 s (-22.88% 🔽)	5.6 s
ECIES encryption	22.94 KB (0%)	459 ms (0%)	877 ms (+12.02% 🔺)	1.4 s
Symmetric encryption	22.39 KB (0%)	448 ms (0%)	1.2 s (+374.71% 🔺)	1.7 s
DNS discovery	72.28 KB (0%)	1.5 s (0%)	2.6 s (+78.63% 🔺)	4.1 s
Peer Exchange discovery	73.79 KB (0%)	1.5 s (0%)	1.7 s (-10.01% 🔽)	3.2 s
Local Peer Cache Discovery	67.63 KB (0%)	1.4 s (0%)	1.9 s (-2.93% 🔽)	3.3 s
Privacy preserving protocols	74.8 KB (0%)	1.5 s (0%)	2.6 s (+44.37% 🔺)	4.1 s
Waku Filter	78.06 KB (0%)	1.6 s (0%)	2.5 s (+61.84% 🔺)	4.1 s
Waku LightPush	75.58 KB (0%)	1.6 s (0%)	2.7 s (+24.01% 🔺)	4.2 s
History retrieval protocols	75.96 KB (0%)	1.6 s (0%)	2 s (+37.93% 🔺)	3.5 s
Deterministic Message Hashing	7.38 KB (0%)	148 ms (0%)	109 ms (-51.44% 🔽)	256 ms

[weboko]

great success!