README: add a section on gif2webp
README: add a section on gif2webp

Change-Id: Ie701da16223df7482f7b017150242ba2d381d0b5

webmproject/libwebp,zofuthan/libwebp,redengineer/libwebp,iniwf/webm.libwebp,imazen/libwebp,iniwf/webm.libwebp,keane83/BLE_IM,comoyo/gonzo-libwebp,comoyo/gonzo-libwebp,rxl194/libwebp,matanbs/webm.libwebp,keane83/BLE_IM,Maria1099/webm.libwebp,yohunl/libwebp,kleopatra999/webm.libwebp,matanbs/webm.libwebp,comoyo/gonzo-libwebp,kleopatra999/webm.libwebp,yohunl/libwebp,keane83/BLE_IM,appunite/libwebp,webmproject/libwebp,kim42083/webm.libwebp,webmproject/libwebp,kim42083/webm.libwebp,Acidburn0zzz/webm.libwebp,Maria1099/webm.libwebp,PKRoma/libwebp,comoyo/gonzo-libwebp,comoyo/gonzo-libwebp,ya7lelkom/libwebp,rxl194/libwebp,imazen/libwebp,PKRoma/libwebp,iniwf/webm.libwebp,Suvarna1488/webm.libwebp,PKRoma/libwebp,redengineer/libwebp,jiehu5114/libwebp,ericmckean/webm.libwebp,kim42083/webm.libwebp,altogother/webm.libwebp,keane83/BLE_IM,gshORTON/webm.libwebp,ttyangf/libwebp,appunite/libwebp,ericmckean/webm.libwebp,Aexyn/libwebp,kalli123/webm.libwebp,kleopatra999/webm.libwebp,kim42083/webm.libwebp,jiehu5114/libwebp,Aexyn/libwebp,abwiz0086/webm.libwebp,Aexyn/libwebp,ttyangf/libwebp,Acidburn0zzz/webm.libwebp,kalli123/webm.libwebp,jiehu5114/libwebp,yohunl/libwebp,gshORTON/webm.libwebp,abwiz0086/webm.libwebp,jacklicn/libwebp,kalli123/webm.libwebp,imazen/libwebp,keane83/BLE_IM,matanbs/webm.libwebp,comoyo/gonzo-libwebp,yohunl/libwebp,jiehu5114/libwebp,zofuthan/libwebp,rxl194/libwebp,webmproject/libwebp,redengineer/libwebp,reimaginemedia/webm.libwebp,PKRoma/libwebp,kim42083/webm.libwebp,ericmckean/webm.libwebp,ya7lelkom/libwebp,Aexyn/libwebp,ericmckean/webm.libwebp,appunite/libwebp,abwiz0086/webm.libwebp,Maria1099/webm.libwebp,ya7lelkom/libwebp,Suvarna1488/webm.libwebp,reimaginemedia/webm.libwebp,Suvarna1488/webm.libwebp,kleopatra999/webm.libwebp,Maria1099/webm.libwebp,matanbs/webm.libwebp,ttyangf/libwebp,redengineer/libwebp,altogother/webm.libwebp,altogother/webm.libwebp,gshORTON/webm.libwebp,comoyo/gonzo-libwebp,zofuthan/libwebp,zofuthan/libwebp,matanbs/webm.libwebp,reimaginemedia/webm.libwebp,imazen/libwebp,PKRoma/libwebp,imazen/libwebp,Aexyn/libwebp,jiehu5114/libwebp,Acidburn0zzz/webm.libwebp,Maria1099/webm.libwebp,ericmckean/webm.libwebp,yohunl/libwebp,jacklicn/libwebp,Acidburn0zzz/webm.libwebp,altogother/webm.libwebp,altogother/webm.libwebp,kleopatra999/webm.libwebp,PKRoma/libwebp,ya7lelkom/libwebp,jacklicn/libwebp,reimaginemedia/webm.libwebp,ttyangf/libwebp,redengineer/libwebp,Acidburn0zzz/webm.libwebp,rxl194/libwebp,appunite/libwebp,Suvarna1488/webm.libwebp,rxl194/libwebp,jacklicn/libwebp,abwiz0086/webm.libwebp,kalli123/webm.libwebp,ttyangf/libwebp,gshORTON/webm.libwebp,iniwf/webm.libwebp,zofuthan/libwebp,reimaginemedia/webm.libwebp,ya7lelkom/libwebp,kalli123/webm.libwebp,jacklicn/libwebp,Suvarna1488/webm.libwebp,abwiz0086/webm.libwebp,appunite/libwebp,appunite/libwebp,webmproject/libwebp,gshORTON/webm.libwebp,iniwf/webm.libwebp