Add `buy medicine` button to plague event.
Add `buy medicine` button to plague event.

Because there is a serious need for medicine, the price
is raised with this button. I felt like it should be even
higher but this will do for now.

Closes #199

asteri0n/adarkroom,bdorer/adarkroom,tehp/adarkroom,Continuities/adarkroom,snazzysanoj/snazzysanoj.github.io,fsladkey/adarkroom,Pioneer11X/adarkroom,doublespeakgames/adarkroom,Tedko/adarkroom,acutesoftware/adarkroom,tehp/adarkroom,snazzysanoj/snazzysanoj.github.io,bdorer/adarkroom,purplemilk/adarkroom,Razynoir/adarkroom,doublespeakgames/adarkroom,snazzysano/adarkroom,fsladkey/adarkroom,Bleyddyn/adarkroom,crafteverywhere/adarkroom,kaisyu/adarkroom,crafteverywhere/adarkroom,ikoan/adarkroom,gerred/adarkroom,as02700/adarkroom,purplemilk/adarkroom,ngosang/adarkroom,kaisyu/adarkroom,kaisyu/adarkroom,asteri0n/adarkroom,doublespeakgames/adarkroom,gerred/adarkroom,Tedko/adarkroom,Continuities/adarkroom,snazzysano/adarkroom,acutesoftware/adarkroom,pablo-new17/adarkroom,ikoan/adarkroom,pablo-new17/adarkroom,snazzysanoj/snazzysanoj.github.io,snazzysano/snazzysano.github.io,ngosang/adarkroom,DDReaper/adarkroom,JamesKent/adarkroom,DDReaper/adarkroom,Pioneer11X/adarkroom,as02700/adarkroom,marty13612/darkroom,snazzysano/snazzysano.github.io,marty13612/darkroom,Razynoir/adarkroom,Bleyddyn/adarkroom,JamesKent/adarkroom,sbakht/adarkroom,sbakht/adarkroom