create branges and merge code example

Example 1: git merge branch to master

$ git checkout master
Switched to branch 'master'
$ git merge iss53
Merge made by the 'recursive' strategy.
index.html |    1 +
1 file changed, 1 insertion(+)

Example 2: merge two branches git

# merge two branches
1] you should be on MainBranch -- git checkout MainBranch
2] then run merge command -- git merge SubBranch