tools: add a script to generate draft release changelog

tools: add a script to generate draft release changelog

This utility script helps in generated formatted and consistent
change log including:
       1- group logs per daemon
       2- standarize daemon names (lowercase, end with d)
       3- capitalize all log lines
       4- no merge commits

caveat: comments are assumed to be in the form

   daemon-name : message

Sample Output:

```
sharpd
    Follow the practice on cli design for json output
    Install route supports nexthop-seg6 (step3)
    Install_routes_helper support zapi_route flags (step1)

snapcraft
    Add missing dependency
    Add pathd to frr snap daemons
    Change base to ubuntu 18.04 and libyang 2.0.7

staticd
    Convert typedef to enum
    Fix distance processing
    Fix late initialization of blackhole type
    Output config using nb callbacks instead of operational data
```

Signed-off-by: Jafar Al-Gharaibeh <jafar@atcorp.com>