feat(RequestContext): add id to RequestContext

[chentsulin]

Add the optional id property to the RequestContext type.

[codecov-commenter]

Codecov Report

Merging #774 into release/1.5 will not change coverage.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##           release/1.5     #774   +/-   ##
============================================
  Coverage        81.07%   81.07%           
============================================
  Files              108      108           
  Lines             4741     4741           
  Branches          1195     1150   -45     
============================================
  Hits              3844     3844           
- Misses             862      869    +7     
+ Partials            35       28    -7     

Impacted Files	Coverage Δ
packages/bottender/src/server/Server.ts	10.46% <0.00%> (ø)
packages/bottender/src/types.ts	100.00% <ø> (ø)
packages/bottender/src/chain.ts	76.92% <0.00%> (ø)
packages/bottender/src/getClient.ts	55.55% <0.00%> (ø)
packages/bottender/src/router/index.ts	90.66% <0.00%> (ø)
packages/create-bottender-app/src/shared/log.ts	0.00% <0.00%> (ø)

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