Update README.md

Fixed formatting

README.md

@@ -49,7 +49,7 @@ _NOTE: set the fetch-depth for `actions/checkout@v2` to be sure you retrieve all
 * **TAG_CONTEXT** *(optional)* - Set the context of the previous tag. Possible values are `repo` (default) or `branch`.
 * **PRERELEASE_SUFFIX** *(optional)* - Suffix for your prerelease versions, `beta` by default. Note this will only be used if a prerelease branch.
 * **VERBOSE** *(optional)* - Print git logs. For some projects these logs may be very large. Possible values are ```true``` (default) and ```false```. 
-* **HEAD_COMMIT** *(optional)* - Commit messages between the last tag and *HEAD_COMMIT* will be used to determine a new version number. Specifying commit is useful when using this action for pull requests - one can set environment variable as follows: HEAD_COMMIT: ${{ github.event.pull_request.head.sha }} to calculate a new version basing on commits from a given PR.
+* **HEAD_COMMIT** *(optional)* - Commit messages between the last tag and *HEAD_COMMIT* will be used to determine a new version number. Specifying commit is useful when using this action for pull requests - one can set environment variable as follows: `HEAD_COMMIT: ${{ github.event.pull_request.head.sha }}` to calculate a new version basing on commits from a given PR.
 
 #### Outputs