event: add FeedOf[T]

[ucwong]

No description provided.

[codecov]

Codecov Report

Merging #1383 (9c18092) into master (8a42644) will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1383      +/-   ##
==========================================
+ Coverage   51.60%   51.69%   +0.09%     
==========================================
  Files         461      462       +1     
  Lines       58199    58265      +66     
==========================================
+ Hits        30034    30123      +89     
+ Misses      25885    25853      -32     
- Partials     2280     2289       +9     

Impacted Files	Coverage Δ
event/feedof.go	100.00% <100.00%> (ø)
accounts/keystore/watch.go	95.83% <0.00%> (-4.17%)	⬇️
rpc/client.go	85.43% <0.00%> (-1.00%)	⬇️
trie/proof.go	75.45% <0.00%> (-0.31%)	⬇️
core/txpool/txpool.go	72.58% <0.00%> (-0.25%)	⬇️
core/rawdb/chain_iterator.go	60.89% <0.00%> (ø)
ctxc/downloader/downloader.go	77.28% <0.00%> (+0.20%)	⬆️
p2p/discover/v5_udp.go	81.59% <0.00%> (+0.44%)	⬆️
trie/trie.go	80.58% <0.00%> (+0.64%)	⬆️
ctxc/filters/api.go	51.33% <0.00%> (+0.66%)	⬆️
... and 3 more