Add .mailmap file

Use .mailmap to fix author names and emails in git log / git shortlog -e.

Fixes #103.
13 jobs for mailmap in 32 minutes and 34 seconds (queued for 5 seconds)
latest
Status Name Job ID Coverage
  Check
passed check #32900

00:00:11

 
  Build
passed build_long: [baseline iso] #33051
fast-single-thread

00:16:38

passed build_long: [baseline netboot] #33052
fast-single-thread

00:16:03

passed build_long: [releng iso] #33053
fast-single-thread

00:32:21

passed build_long: [releng netboot] #33054
fast-single-thread

00:31:27

passed build_short: [baseline bootstrap] #33049

00:11:39

passed build_short: [releng bootstrap] #33050

00:12:24

failed build_long: [baseline iso] #32903
fast-single-thread

00:08:33

failed build_long: [baseline netboot] #32904
fast-single-thread

00:07:20

failed build_long: [releng iso] #32905
fast-single-thread

00:08:23

failed build_long: [releng netboot] #32906
fast-single-thread

00:07:07

failed build_short: [baseline bootstrap] #32901

00:08:02

failed build_short: [releng bootstrap] #32902

00:08:03