README.rst: Update the link for coala Usage

[budukhyash]

The link for the coala-bears usage further navigates to this which has no information about how to use coala. One can do either of the following:

• Update the link so that it navigates to the coala documentation.

• Add usage information in the README.rst file located here.

Maintainers can suggest the correct way.

[mohit2872]

can you assign this issue to me?

[mohit2872]

@jayvdb

[iBvishal]

HelloWorld! if this issue is still open I want to work on that.

[yash-kedia]

hey can this issue be assigned to me

[rachitgoel05]

Can I be assigned this issue. @jayvdb

[Dilshaad21]

I am taking this issue since no one has submitted any pr for this issue yet.

[KVGarg]

@Dilshaad21 You've already worked on a newcomer issue. Please follow the newcomers guide!

[Nishant-Ingle]

@jayvdb @li-boxuan I would like to fix this issue