Bump version number to 1.2, add release notes

[alice-i-cecile]

We should ship #21.

[BenjaminBrienen]

 techn0@IO  ~/source/atomicow   main  git status
On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean
 techn0@IO  ~/source/atomicow   main  cargo semver-checks --baseline-version 1.0.0 --all-features          
    Building atomicow v1.1.0 (current)
       Built [   0.207s] (current)
     Parsing atomicow v1.1.0 (current)
      Parsed [   0.001s] (current)
     Parsing atomicow v1.0.0 (baseline, cached)
      Parsed [   0.001s] (baseline)
    Checking atomicow v1.0.0 -> v1.1.0 (minor change)
     Checked [   0.002s] 196 checks: 196 pass, 56 skip
     Summary no semver update required
    Finished [   0.372s] atomicow
 techn0@IO  ~/source/atomicow   main  gh pr checkout 22
branch '1.2-bump' set up to track 'origin/1.2-bump'.
Switched to a new branch '1.2-bump'
 techn0@IO  ~/source/atomicow   1.2-bump  cargo semver-checks                                        
    Building atomicow v1.2.0 (current)
       Built [   0.251s] (current)
     Parsing atomicow v1.2.0 (current)
      Parsed [   0.001s] (current)
     Parsing atomicow v1.1.0 (baseline, cached)
      Parsed [   0.001s] (baseline)
    Checking atomicow v1.1.0 -> v1.2.0 (minor change)
     Checked [   0.002s] 196 checks: 196 pass, 56 skip
     Summary no semver update required
    Finished [   0.409s] atomicow